Hi,

I am investigating the use of dovecot for a voicemail storage system (which is effectively a SMTP/POP3 system), which we want to use replication to give us some resilience.

Tests have mostly been on dovecot 2.3.8 (9df20d2db) - as packaged on Centos 8 - but I have also used a couple of similar versions on different platforms, so this is not a specific build problem.

The platform has replication working, over an SSL TCP link, for delivery.

With the pop3 configuration as default as is possible (although the mail_plugins are explicitly included into the protocol sections to ensure notify and replication is called for), any pop3 delete operation does not cause a notify or replication operation.  The two servers show the mailboxes in a different state up until something else prods a replication into progress.

I would suggest that a pop3 delete/expunge of a message should be flagged as a mailbox change can cause a notify/replication, and that the current behaviour is a bug.

There are workarounds to this, and I am considering adding a note to the wiki page https://wiki.dovecot.org/Replication to flag this - not sure what your wiki editing policy is.

# Workaround 1 - Change pop3 deletion to set a flag

If the setting pop3_deleted_flag = '$POP3Deleted'

is added, then rather than the mail being deleted, it is flagged, and this change causes a notification and replication to the other server.

However since the mail is not actually deleted, you additionally need another (cron?) task to periodically remove flagged mail, for example:-

    doveadm expunge  -A MAILBOX inbox KEYWORD '$POP3Deleted'

# Workaround 2 - Use Lazy Expunge

You can use the lazy_expunge plugin - this has the same effect, and automates the removal of the messages after a period of time.

    https://doc.dovecot.org/configuration_manual/lazy_expunge_plugin/

For example, you can set the following changed config fragments:-

    mail_plugins = $mail_plugins notify replication lazy_expunge

    namespace inbox { separator = / prefix = inbox = yes

        # automatic lazy expunge mailbox mailbox .EXPUNGED { autoexpunge = 3 days autoexpunge_max_mails = 1000 } }

    plugin { # Move messages to an .EXPUNGED mailbox lazy_expunge = .EXPUNGED }

    Nigel.

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[ Nigel Metheringham --------------------------- nigel@dotdot.cloud ] [              Ellipsis Intangible Cloudy Technologies              ]