Online Mailbox Format Conversion
--------------------------------

This page aims to help with the tasks around planned mailbox migrations to e.g.
mdbox. To perform this exercise with minimum service interruption a Postfix
check can be implemented to put mail for the accounts to be migrated on HOLD:

Postfix main.cf
---------------

---%<-------------------------------------------------------------------------
smtpd_recipient_restrictions =
 [...]
 check_recipient_access hash:/etc/postfix/recipient_maintenance,
 permit_mynetworks,
 reject_unauth_destination
---%<-------------------------------------------------------------------------

/etc/postfix/recipient_maintenance
----------------------------------

---%<-------------------------------------------------------------------------
user@domain.tld HOLD Planned maintenance
user1@domain.tld HOLD Planned maintenance
user2@domain.tld HOLD Planned maintenance
[...]
---%<-------------------------------------------------------------------------

Virtual Domain Aliases in Postfix can be easily used to populate the *List of
Recipients* to be converted (and to be queued on HOLD). The following basic
script helps populating the database and needs to be adapted to the actual
alias location:

---%<-------------------------------------------------------------------------
#!/bin/bash
set -e
ALIASES="/etc/postfix/virtual"
MAINTALIASES="/etc/postfix/recipient_maintenance"

doveadm user $1 || { echo 'user query failed.'; exit 1; }

sed -e "s/\(.*\)$1/\1/;s/[ \t]*$//; s/$/ HOLD Planned maintenance: account=$1/"
$ALIASES >>$MAINTALIASES
grep $1 $MAINTALIASES
postmap $MAINTALIASES
echo '[ Complete ]'
---%<-------------------------------------------------------------------------

Usage:

---%<-------------------------------------------------------------------------
$ maintalias.sh user@domain.tld
---%<-------------------------------------------------------------------------

Finally running *postmap recipient_maintenance* will create the database (in
case this part is not scripted).

Actual Migration
----------------

Disable new logins for the users by adding 'allow_nets=' to their userdb
records, effectively disallowing ALL nets. Close open sessions if any:

---%<-------------------------------------------------------------------------
$ doveadm who <user>
$ doveadm kick <user>
---%<-------------------------------------------------------------------------

Convert the mailbox using the backup option:

---%<-------------------------------------------------------------------------
$ dsync -u user@domain.tld backup mdbox:~/mdbox
---%<-------------------------------------------------------------------------

Adjust userdb entries (if required) to reflect new 'mail_location'. Clear the
'recipient_maintenance' DB and undo 'allow_nets=' entries for the migrated
users.

Finally release and requeue all mail previously held:

---%<-------------------------------------------------------------------------
$ postsuper -r [ALL]
$ postqueue -f
---%<-------------------------------------------------------------------------

(This file was created from the wiki on 2019-06-19 12:42)