Accounts and aliases#

A plMail account is one mailbox you have somewhere else — an IMAP, POP3 or JMAP server, Gmail, or Outlook — that plMail signs into and syncs. You can connect as many as you like; they sync independently and read as one inbox.

Everything on this page lives under Settings → Mail accounts, except where it says otherwise.

Adding an IMAP mailbox#

Settings → Mail accounts → Add account, on the IMAP / SMTP tab. Enter the address and password. The Provider dropdown carries the settings for a long list of common providers and is matched against the domain you typed, so for most mailboxes the host, port and encryption fill themselves in; several entries also carry a note about something the provider requires, such as IMAP needing to be switched on in their web interface first. If yours is not listed, take the IMAP and SMTP details from your provider's documentation.

A blank form starts on port 993 with SSL for incoming and port 587 with STARTTLS for outgoing, which is what nearly every provider wants.

Labels asks where the labels you give this account's mail are kept: Only in plMail, the default, or On the server too, as IMAP keywords, so other mail apps show them too. See Labels as keywords; the switch is in the account's folders for later.

Test connection probes IMAP and SMTP separately and reports each. Saving does not depend on it, but an account that stores cleanly and cannot log in is the failure worth catching now rather than at the first sync, so the probe runs again on save and its outcome is remembered on the account.

The first sync starts immediately, and the account's existing mail is then brought in newest first: the most recent of the Inbox within a minute or so, the rest of the Inbox after it, then Sent, Drafts and your own folders, the archive, and Spam and the bin last. Mail that arrives while this runs is not held up by it. A chip beside the search box says Importing for as long as an account is, and opens a list with how much of each is in and which folder it is on; if nothing has moved for a while it says Waiting to continue, and an account that cannot be reached is listed under Account health.

After that, plMail holds an IMAP IDLE connection to each mailbox and syncs the moment something changes, with a scheduled sweep every fifteen minutes behind it.

See IMAP and SMTP for the settings servers disagree about.

Adding a POP3 mailbox#

Some providers serve POP3 and SMTP and no IMAP at all. For those, choose POP3 under Incoming protocol on the same form; the incoming port starts at 995, which is POP3 over SSL. Picking a provider from the Provider list fills in its POP3 server where plMail knows one; a provider without one, such as iCloud, switches the form back to IMAP, and POP3 stays greyed out until you clear the provider or pick another.

POP3 has one mailbox and nothing else: no folders, no flags, and no way to tell the server anything but "delete this". So in plMail a POP3 account is a single inbox. Reading, starring, labelling and moving mail all happen here and stay here, and the next sync does not undo them. Mail you send is labelled Sent in plMail; the server has nowhere to keep a copy. There is no IDLE either, so new mail arrives with the sweep every fifteen minutes, or straight away with the sync button.

Each message is recognised by its UIDL, the server's own name for it, so mail is never fetched twice. The first sync of a large mailbox brings in a few hundred messages per sync, newest first.

After fetching decides what happens to the server's copy. Leave it on the server is the default. Choose Delete it from the server and a message is deleted there once it is stored in plMail, and only then. A message plMail could not fetch or store stays on the server whatever this says. Deleting frees space at your provider, but plMail's copy is then the only one.

You can switch an existing account between IMAP and POP3 on its edit form. Its mail stays: the next sync recognises what plMail already holds and does not store it again — by its Message-ID, or for the rare message without one, by its sender, subject and date. Folders other than the inbox keep their mail when an account becomes POP3, and stop syncing.

Adding a JMAP account#

A server that speaks JMAP — Stalwart, Fastmail, Cyrus — is added on the same form: choose JMAP under Incoming protocol and give the server's host name and an app password, or an API token with The password is an API token ticked. One login brings the account's mail, and its calendars and contacts too where the server has them, and sending goes through the server unless it offers no submission — which is why the form folds the SMTP fields away under JMAP, behind My server does not send over JMAP — use SMTP. Fastmail is in the Provider list with its JMAP server. Changes on the server arrive as they happen. An existing account can be switched between IMAP and JMAP on its edit form, keeping its mail.

See JMAP for the rest.

Adding Gmail or Outlook#

Both are OAuth, so an administrator has to register an application with the provider before the button does anything. Once that is done, Add account offers Continue with Google and Continue with Microsoft on the OAuth tab, and the whole flow is the provider's own consent screen — no password is stored here at all.

Grant everything the consent screen asks for. Google's screen lists the permissions as separate tick boxes and lets you decline any of them — and declining one does not fail the sign-in. The account connects, plMail says so, and the part you withheld quietly does not work: calendars that never sync, or mail where marking read and archiving appear to work on screen, are refused by Google, and are undone by the next sync. A Microsoft tenant can withhold the same permissions by policy.

plMail now compares what it was given against what it asked for and puts a card on Account health when they differ, with a button to connect again and grant the rest. If you connected an account before this existed, the card appears the first time the account refreshes its sign-in, or the first time a change is refused.

Microsoft accounts go through Graph rather than IMAP. That is deliberate: Exchange Online treats IMAP as legacy authentication and blocks it in any tenant running Security Defaults.

The registration itself — which console, which redirect URI, which scopes — is on Google and Microsoft. Where the credentials go is a choice: an administrator can enter them in Admin → Integrations under Mail sign-in, or leave them in the environment as GOOGLE_OAUTH_* and MICROSOFT_OAUTH_*, which is what an older installation will already be doing. See Administration.

An OAuth account has no editable form here. There is nothing to edit — no password, no host — so it is managed by connecting and disconnecting rather than by a settings page.

The account list#

Accounts are listed in your own order and can be dragged to reorder. The order is cosmetic. It decides where a row sits and nothing else.

Which account a new message is composed from is a separate, stored choice: the primary account, marked Primary on its row and set by Make primary on any other. This used to be the same thing — the top row was the primary — which meant tidying the list silently changed the address you send from, with nothing on screen saying so. Two decisions, two controls.

The coloured dot beside each account is its identity colour: the same tone that account's messages wear in the unified lists, so two accounts can be told apart at a glance in a list that mixes them. It is handed out when the account is added — the first of eight colours not already in use — and from then on it changes only when you change it. Reordering the list does not repaint it, and it is not a status light. Whether an account is actually working is answered on Account health, which is the one place that claims to answer it.

You change it with the coloured swatch on the account's row, which opens the palette of eight. That control is on every account, Gmail and Outlook ones included, which is why it is not a field in Edit account: that form is closed to them. The sidebar dot changes at once, and every list you open afterwards wears the new colour on that account's messages; a list already open in another tab repaints when it reloads. Choosing a colour another account already wears is allowed, so two accounts can be made a pair.

Each row offers:

The primary flag is never lost. Removing the account that held it hands it to another, and the very first account you add is primary because there is nothing for it to inherit from.

Removing an account deletes its synced mail from plMail's database and nothing at the provider. It also tries to tear down any push registration it had, so nothing is left pointing at an account that no longer exists.

Anything else that takes a registration away now hands it back to the provider the same way — deleting a calendar, unticking one, disconnecting a connection, and an administrator's data reset. The attempt is best-effort: a provider that refuses, that has already expired the channel, or that cannot be reached is stepped over rather than blocking the removal, because a reset that will not run because Google is unreachable is a worse outcome than a channel that lapses on its own within the week.

On the edit form, leaving the password field blank keeps the stored one.

Per-account settings#

The controls under each account row each re-render on their own rather than reloading the whole list.

Instant delivery#

Instant delivery switches an account between push and scheduled polling. It appears only for Gmail and Microsoft — a plain IMAP mailbox has no push manager, and IDLE already gives it the same effect.

Turning it on registers with the provider there and then. If registration fails the switch goes back off, so the interface never claims push is working while nothing is being delivered, and the reason is spelled out:

• Gmail — Google refused the watch. Check that GMAIL_PUBSUB_TOPIC names a topic that exists and that the topic grants gmail-api-push@system.gserviceaccount.com the Pub/Sub Publisher role. Note the -push: gmail-api@system.gserviceaccount.com is not an address Google publishes from, so a topic granted exactly that will never deliver a single notification.
• Microsoft — Microsoft could not reach this server over HTTPS. Check the reverse proxy and APP_PUBLIC_URL.

Either way the account keeps syncing on a schedule. Push is an optimisation, never the only path.

The badge next to it reads Push when registrations are healthy, Scheduled when it is off, and one of two things when it is broken:

• Push (expired) — the registration's own expiry passed and nothing renewed it. Renewal runs daily on its own, so this usually means the scheduled-task worker has stopped.
• Push (not delivering) — the registration is alive and unexpired, and mail has arrived that it never announced. For Gmail that points at the Pub/Sub push subscription being missing or pointing somewhere else; for Microsoft, at a subscription that has lapsed.

Re-register push is the button for both, and Account health explains which of the two you are looking at and shows the dates it decided from.

Where push is not available on this server at all, the control says so rather than offering a switch that cannot work.

Labels at the provider#

On Gmail and Microsoft, labels you create, rename or delete are mirrored to the provider, whether the change came from the web UI or from a JMAP client. There is no switch for it: it used to be one, off by default, and all it bought was an organisation that existed only in plMail and vanished the moment you opened Gmail. It only ever affects changes made from then on; labels that already exist are not pushed retroactively.

On a plain IMAP account a label never creates, renames or deletes a folder on the server, and it never moves mail. Folders are made, renamed and deleted in the account's own folder list — see Folders. Where a label goes instead is the next section.

Labels as keywords#

IMAP has tags of its own: keywords, which a server keeps on each message beside \Seen and \Flagged, and which other mail apps show — Thunderbird as its tags, for one. Labels as keywords, at the top of an IMAP account's folder list, puts your labels there. It is off by default, and then a label on IMAP mail stays in plMail, as it always has. Adding an IMAP account asks the same question.

Switched on, putting a label on a conversation writes it to the server as a keyword on each of its messages, and taking it off removes it. A keyword set or cleared in another mail app puts the label on or takes it off here, within seconds when plMail is idling on the folder and at the next sync otherwise; a keyword plMail has not seen before becomes a new label. Capitals do not count, as they do not for IMAP: a keyword paperless that another tool sets puts your label Paperless on, not a second label beside it. Labels still never move mail, and a label that is a folder on the account stays a folder.

Switching it on asks each folder whether the server keeps keywords there, and the list says what it answered: This server keeps keywords, This server keeps no keywords (labels then stay in plMail on that account), or not asked yet. Every label's dialog says, per IMAP account, where it is kept: a folder, a keyword, or only in plMail, and why.

A label's name becomes a keyword as it is when it can — "Work", "Invoices/2025" — so it matches what other mail apps write. A name with spaces or other characters a keyword cannot hold is written in the encoding IMAP uses for folder names ("Follow up" is Follow&ACA-up), which plMail reads back as the same name. Keywords that mean something to mail apps — $Junk, $NotJunk, $Forwarded, $MDNSent, $Phishing, $Important, Thunderbird's $label1–$label5 — are never read as labels.

Only changes made after switching it on are written; labels already on mail are not pushed in bulk. The other way round, switching it on reads the keywords the account's mail already carries, once, in the background: mail that had a keyword before the switch went on gets its label too.

Labels as Outlook categories#

On a Microsoft account a label is an Outlook category, unless it came from an Exchange folder, in which case it is that folder. Putting a label on a conversation puts the category on each of its messages in Exchange, and taking it off takes it off; creating a label here creates the category in Outlook's category list, in the label's colour. Labels never move mail, and a label that is a folder stays a folder.

What comes back from Outlook is the other half, and it depends on Follow Outlook categories, the tags icon on a Microsoft account's row. It is off by default, and then plMail behaves as it always has: categories are read when a message first arrives, and a category put on or taken off in Outlook afterwards changes nothing here. Switched on, such a change puts the label on or takes it off in plMail at the next sync, and a category plMail has not seen before becomes a new label. Only changes count: plMail remembers which categories Exchange last held for each message, and a message is changed here only where Exchange's list differs from that. A label you put on in plMail and Exchange never had is therefore left alone, not taken off.

Turning it on makes plMail list every folder of that account once more, because the record of where each folder's sync had got to was started without categories and cannot be widened. Nothing is fetched twice — mail already here is recognised — but on a large mailbox that first pass takes a while. Turning it off again costs nothing.

The label dialog says, per Microsoft account, where the label is kept: a folder, or an Outlook category, and whether Outlook's changes to it are followed.

A category has no identity but its name — the name is what is written onto each message. So renaming a label does two things: the category in Outlook's list gets the new name, and every message plMail holds that carries the old name is pushed again so it carries the new one. That second half is the same question Outlook's own rename dialog asks; here it is answered yes, because the alternative is a mailbox where the label exists twice — once as a category and once as loose text on the mail that used to have it. A label on thousands of messages therefore means thousands of updates, sent in the background. Microsoft documents a category's name as fixed once made; where Exchange refuses the rename, plMail makes the category under the new name and deletes the old one, which ends in the same place.

Deleting a label deletes the category from Outlook's list. Exchange leaves the name on each message as plain text, which Outlook shows without a colour, until something next changes that message's labels in plMail.

Labels that ARE backed by a real Exchange folder — the ones that came from one — are renamed as folders instead, and nothing has to be re-tagged.

Folders#

Folders opens the account's folders as the server has them: the same tree, nested the same way, whatever it looks like. A folder is a place — each message is in exactly one folder of its account — and this list is where folders are managed. It appears only for IMAP accounts: a Gmail or Microsoft account syncs through its provider's API and has no folder list here. A folder the server has stopped listing is not shown.

The same dialog is on the account in the sidebar's ACCOUNTS section. An IMAP account's row has a ⋯ button whose menu offers New folder…, which opens the form for that account, and Folders…, which opens the list. Expand the account and its folders end with + New folder; with a mouse, hovering one of your own folders there shows a pencil that opens its rename. In the LABELS section a label that is a folder on an IMAP account wears a folder in its colour instead of a dot, and its tooltip names the account, so a folder and a plain label can be told apart.

Syncing#

Each folder has a switch, and every folder starts on. Switching one off stops plMail fetching it: the mail already stored stays where it is, and switching the folder back on resumes from where it stopped. The inbox has no switch, because a client that has stopped fetching its inbox is not a client — to stop an account altogether, disable it.

Two kinds of folder start off: Starred, and All Mail on an account that also has an Archive folder — Proton Mail Bridge has both. They are the server's view of mail it keeps in your other folders, and fetching them would show every message twice. The copies of mail kept elsewhere that plMail stored from them before are removed over the next syncs; mail only they hold stays. On Gmail over IMAP All Mail stays on, because archived mail lives there and nowhere else. Switching either back on fetches the copies it had removed again.

Nested folders are indented under their parent. A folder that only groups others and holds no mail of its own — Gmail's [Gmail], for one — is listed greyed out with its switch off and disabled: the server will not open it, so there is nothing to fetch.

The list names a folder the way the server does. The inbox and the other system folders read as they do in the sidebar ("Drafts", "Trash"), so the same folder is not called two things.

New folder#

New folder asks for a name and for where it goes: Top level, or inside any folder the server listed. It starts on the place you chose last time on that account, here or in Make it a folder, so a server whose own folders sit under the inbox is answered once. plMail makes the folder on the server, so it appears in every mail app that reads the account, subscribes to it, and shows it in the sidebar like the account's other folders. There a folder sits inside the folder it is in on the server, the Inbox included, and a folder with folders in it can be collapsed on its own.

You type a name, never a path. Where the top level is and which character separates a folder from the folders inside it are the server's to say, and plMail asks it: on most servers the top level is the top, and on servers that keep everything under the inbox (INBOX.Name) a top-level folder goes there too, where your other mail apps expect it. Names in any script work, "Bücher" or "Café". A folder that is already on the server under that name is not an error: plMail takes it as made.

A name is refused before the server is asked when it cannot be a folder there:

• it contains the server's separator — / on most servers, . on some. A folder called "v1.2" on a . server would silently become a folder "2" inside a folder "v1";
• it contains * or %, which other mail apps cannot list reliably, or a line break;
• it is "INBOX" at the top level, which every server reserves for the inbox.

When it works, the dialog closes, the usual notice at the bottom of the screen says so, and the folder is in the sidebar at once. A name the server itself refuses — one it does not allow, a folder that already exists when you rename, a quota — is shown with the server's own words, and nothing changes.

Rename and delete#

Your own folders have a pencil (Rename folder …) and a bin (Delete folder …) beside their switch.

Rename gives the folder a new name where it is. The server renames the folders inside it along with it, and plMail follows at once: its mail stays where it was, and its label in the sidebar keeps everything filed under it, under the new name. A label that a folder on another of your accounts shares is not renamed from here, because it is that folder's name as well; the renamed folder gets a label of its new name instead. Some servers give a renamed folder a new identity, so plMail syncs the account straight afterwards.

Delete removes a folder from the server, and only an empty one: no mail in it, neither in plMail nor on the server, and no folders inside it. Anything else is refused with the reason — move the mail or the folders out first. Deleting a folder never deletes mail. Its label goes with it when nothing else is left on the label.

The inbox, Sent, Drafts, Trash, Junk and Archive have neither button. plMail never renames or deletes them: your other mail apps and plMail's own sending, archiving and spam handling find them by name, or by the role the server gives them, and a renamed Sent folder is one nothing files into.

A folder made, renamed or deleted in another mail app shows up here after the next sync. A folder renamed elsewhere keeps its mail and, unless another account shares it, its label, under the new name.

Sending aliases#

Settings → Aliases lists the addresses each account sends and receives as. Refresh from provider asks the account what it knows about; Add takes one you type yourself.

Each address is Primary, active, or disabled. The primary is the default sender for that account and cannot be disabled or removed — make another one primary first, which demotes it. Disabled addresses stay on the list and stop being offered in the compose window.

The From selector in the compose window lists accounts and aliases together, so sending as an alias is one choice rather than two.

A reply opens on the address the mail was sent to. Mail that came in for an alias is answered from that alias, without you picking it; mail that names none of the account's addresses — a list, a Bcc the server left no trace of — is answered from the primary one. Answering mail you sent yourself keeps the address you sent it from. The selector is still there to change it.

The name an address sends under#

Under each address is a field for the sender name: what the recipient sees beside the address. Left empty, the address sends under the account's name, which is what the field shows greyed out. A family address on a personal account can be "Mr and Mrs Smith" while the account stays "John Smith". The From selector shows the same name the mail goes out with.

Catch-all domains#

If your provider delivers every address at a domain to this mailbox, add the domain under Catch-all domains. plMail then treats any address at that domain as yours for answering: a reply to mail sent to anything@example.com goes out from anything@example.com, with the account's name and signature, and you are left out of your own reply-all. A meeting invitation sent to such an address is yours to answer, and the answer goes back from it. No alias has to be added first, and nothing changes for mail that arrives.

Not every address at the domain is treated as you. A catch-all catches what has no mailbox of its own, and on a family or company domain other people have one: anna@example.com is at your catch-all domain and is somebody else. So an address counts as yours only for a mail it reached you by — the address your server recorded delivering it to, or, where the server recorded none, the addresses at that domain in To and Cc. Anna stays in your reply-all, her mail is answered to her rather than as her, and an invitation naming her is not offered to you. Where a mail names both of you and carries no delivery record, plMail cannot tell which was yours and treats both as you.

Three things it does not do. It is one domain exactly — example.com does not cover mail.example.com. It applies to replies and forwards; a new message is still sent from an address on the list above. And it is not offered for Gmail or Outlook accounts, which send only as addresses the provider itself knows about and rewrite or refuse any other. plMail does not check that the domain really is a catch-all, or that your provider lets you send from it: that is between you and the provider, and a wrong entry shows up as a refused or rewritten sender on the first reply.

One caveat plMail states on the page itself: Outlook sends as the account's primary alias regardless of what you choose here. That is Microsoft's behaviour, changed in your Microsoft account settings, not here.

Gmail collecting mail for another account (Gmailify)#

Gmail can fetch the mail of another address into your Gmail inbox. When that other address is connected here as well, every message reaches plMail twice: once through Gmail and once through the other account's own IMAP sync. plMail files such mail under the other account and merges the two copies into one, so a message is listed once. The merged message is still the other account's: its IMAP folder decides whether it is in the Inbox, the bin or another folder, whatever Gmail did with its own copy. Labels you give it in Gmail show here, and archiving, starring or labelling it here is also sent to Gmail.

Under each Gmail account on this page, File mail for my other accounts under them turns this on or off. It is on unless you turn it off. Turn it off once Gmail no longer collects that mail, typically after a domain has moved from Gmail to an IMAP provider of its own. Otherwise Gmail's old and late copies keep being matched to the other account. With it off:

• The Gmail account keeps only mail addressed to itself. Mail it has for other addresses is not stored again.
• The other account's own copies stop following Gmail. They lose the labels Gmail put on them, and a change you make to them is no longer sent to Gmail. The mail itself stays where its IMAP folder has it. This runs in the background, so on a mailbox that has collected mail for years it can take a few minutes after the switch is turned off.
• Mail that Gmail filed under the other account, and that the other account's IMAP server never had, stays as it is and keeps following Gmail. Gmail is the only place that mail exists.

Best turned off once Gmail has stopped collecting. While Gmail still collects the other address's mail, plMail tells that mail apart by its recipients: a message whose To or Cc names the other address, and not the Gmail address, is left to the other account, even though Gmail stamps its own address on it as the place it was delivered. A message Bcc'd to the other address names nobody, so it looks like the Gmail account's own mail and is kept on both accounts. Mailing lists and newsletters often arrive that way. Stop the collecting in Gmail (Settings → Accounts → Check mail from other accounts) and those duplicates stop too.

Turning it back on changes nothing that is already stored. Mail that arrives afterwards is matched again, and so is an older message once Gmail reports a change to it.

Mail moved by Gmail before v0.3.9. Earlier versions moved the other account's copy wherever Gmail moved its own. Mail trashed or archived in Gmail showed in plMail's bin or archive, although the IMAP server still had it in its Inbox. To put that mail back where its IMAP folder has it, an administrator runs:

php bin/console app:backfill gmailify-placement

Run it while the workers are quiet. A move you make in plMail updates the labels first and the IMAP folder a moment later, and a message caught in between would briefly go back to its old folder. Mail that those earlier versions removed because Gmail had emptied it from its bin is not brought back by this. The IMAP sync only fetches mail newer than what it already has.

What each address does by default#

Two settings hang off the alias list rather than off the account, because they are properties of the address people see rather than of the mailbox it lives in.

Compose defaults, under the alias list on the same page, currently holds one control per address: what that address does when a sender asks to be told their mail was read. The default is Never send, and it is worth understanding before changing it — see Read receipts.

Settings → Signatures is its own section. The account has a signature, and any of its addresses can either inherit it, replace it, or deliberately sign with nothing. The three states and what the compose window does with them are in Composing.

Where to read further#

• IMAP and SMTP, Google, Microsoft — the exact provider-side setup.
• Account health — what is broken, and the repairs that keep your mail.
• Mail ingest — what a sync run actually does.
• Configuration reference — APP_PUBLIC_URL, the OAuth variables and the Pub/Sub ones.
• Troubleshooting — when mail stops arriving.

Things that bite#

Reordering the list no longer changes which account you send from. It used to, and an install upgraded from an older version keeps whichever account was first at the moment it upgraded. If Compose starts from the wrong address, the fix is Make primary on the right one — dragging it to the top will not do it.

A dead sign-in does not have to mean re-adding the account. Deleting a broken account and adding it again is the reflex, and it costs you every message synced from it. Settings → Account health offers a reconnect that keeps the mailbox; see Account health.

A large mailbox takes a while to arrive in full. plMail syncs everything the account holds; there is no setting that bounds it. The newest mail lands first, and the rest follows over the following runs, so an account added minutes ago is usable long before it is complete.

Testing the connection on an existing account needs a password in the field. A blank password means "keep the stored one" on the edit form, and the tester can only resolve that once the account id has reached it — otherwise it says so rather than testing with nothing.

Removing an account deletes its synced mail from plMail. Nothing is removed at the provider, and re-adding the account syncs it again from scratch.

A Google consent screen lets the user untick calendar access while allowing mail. The account connects, mail works, and no calendars appear. Reconnecting with the box left ticked is the fix.

Push failing is not an error state. A self-hosted install may have no publicly reachable HTTPS address at all. Registration failing means "stay on polling", and the fifteen-minute sweep is unaffected.

On some servers a folder renamed in another mail app comes back as a new folder. plMail recognises a rename by the folder's UIDVALIDITY, which a rename keeps. Stalwart 0.11 answers STATUS with a different number from the one it gives when the folder is opened, so a folder renamed there in another app arrives as a new folder, its mail is fetched again, and the old one is removed once it has been missing for three syncs and a day. A rename made in plMail is not affected.

The server decides which folders are system folders, and not every server says. A folder the server marks as Sent, Trash, Junk, Drafts or Archive, or one with a well-known name such as "Sent Items" or "Gesendet", is protected from rename and delete. A folder whose name plMail does not know and that the server does not mark — Stalwart's "Junk Mail" — is treated as your own.

Renaming or deleting a label does not touch keywords already on the server. A renamed label's mail keeps the old keyword, and a deleted label's keyword stays where it is, in plMail and in other mail apps. Putting the renamed label on again writes the new keyword; the old one can be removed in another mail app, which takes the old label off here too.

Other mail apps decide which keywords they show. Thunderbird shows a keyword as a tag only once a tag of that name exists there; until then the keyword is on the message and not on screen.

Mail plMail never synced keeps an Outlook category's old name. Renaming a label re-tags the messages plMail holds; anything Exchange has that plMail does not carries the old name as plain text, which Outlook shows without a colour.

Follow Outlook categories reads only changes. Mail that already had a category in Outlook when it arrived here has that label; a category added in Outlook before the switch was turned on, to mail already here, is not picked up afterwards. Put it on in plMail, or take it off and on again in Outlook.

A message moved in another mail client into a folder that is switched off looks, to plMail, like one that left the account. The check that lets mail deleted elsewhere disappear from plMail only looks in the folders that are switched on, so a message filed elsewhere into a folder plMail is not fetching disappears here although it still exists on the server. That is the switch doing what it says, and nothing is lost: switch the folder on and plMail fetches the message again. A move made inside plMail is different — plMail knows where it put the message and keeps its copy.