# External mail accounts

External IMAP and POP3 credentials are stored in
`external-accounts.sqlite`. Credential values are encrypted with AES-256-GCM;
the per-installation master key is stored separately as
`external-accounts.key` in Bongo's DBF directory. Both files are restricted to
the Bongo service account.

Back up the database and master key together. A database backup without the
matching key cannot decrypt external-account credentials. Do not copy the key
to another installation unless the associated database is moved as well.

The collector verifies TLS certificates and host names by default. Provider
passwords are never included in URLs or log messages. Existing plaintext
credential records from early 0.7 development versions are encrypted
automatically the next time they are read.

For an internal provider signed by a private certificate authority, set
`ca_file` in `/etc/bongo/config.d/collector` to the absolute path of a PEM CA
bundle and run `bongo-admin config sync`. Certificate and host-name
verification remain enabled. Prefer installing a site-wide CA through the
operating system trust store when possible. `BONGO_COLLECTOR_CAINFO` remains
available as a test-only environment override.

Remote deletion policies are `never`, `after_import`, and `after_days`.
Messages are recorded as imported only after Bongo's durable Queue accepts and
commits the complete message. The normal antivirus, antispam, Sieve/rules,
quota, and Store delivery pipeline owns it from that point onward. A failed
remote deletion does not cause the message to be delivered again; the
collector retries the deletion during a later poll.

`maximum_pending_messages` and
`maximum_pending_messages_per_user` in the suffixless `collector`
configuration bound the number of externally collected messages that may be
waiting anywhere in Bongo's Queue. Their defaults are 10000 globally and 1000
per local user. The per-user value must not exceed the global value. The
collector checks both limits before fetching each previously unseen message;
when either limit is reached, it records backpressure on the external account
and leaves that message at the provider. Successfully delivered Queue entries
no longer count toward either limit, so collection resumes on a later poll
after the user or administrator has freed the bottleneck.

The authenticated Queue command `QCOUNT COLLECTED [user]` supplies this
pending count without treating unrelated SMTP or LMTP traffic as collector
load. Administrators can inspect the same values with:

```sh
bongo-queuetool collected-count
bongo-queuetool collected-count username
```