[deliver to local Dovecot replica when SMTP is down]
Noel Jones:
> Maybe use local (split DNS) MX records records to deliver locally
> when the remote vpn connection Postfix-B is unavailable. This would
> probably require a second local postfix instance to receive the mail
> for dovecot since MX records require an SMTP hop.
>
> Then use a doveadmin command from cron to sync/move any local mail
> to the remote B instance periodically.
>
> Actually, my first thought is if the vpn is frequently down, then
> *that's* the problem to fix. Or just keep all the mail on the
> cloud-A and access IMAP over the internet.
If the outages are persistent, then it may make sense to temporarily
change Postfix configuration.
Example 1:
This could be manual or automatic.
VPN down: Update transport_maps to route the domain to the local
Dovecot replica.
VPN up: Update transport_maps to route the domain to the cloud
server.
To update a Berkeley DB transport map safely, see
http://www.postfix.org/DATABASE_README.html#safe_db
After each map update, "postfix reload" and "postqueue -f".
Example 2:
This is an 'automatic' solution.
Configure a dynamic transport map (transport_maps = socketmap:blah)
that responds after checking the VPN status. Problem is, the
Postfix transport daemon has a one-element in-memory cache, and
if all queries are for the same domain, then it will reply from
cache instead of querying the transport map.
Wietse
