Re: backup server to send email

[Dan MacNeil <dan@thecsl.org>]

> Cherubini Enrico wrote:
> > Good day,
> > I would like to know if there is any way for postfix to send email to a
> > smarthost server (a backup server) if something fail, ie disk full,

If I understand your question correctly. If your main mailserver is 
unavailable, you want another mailserver to accept mail on your behalf 
until the main server is back.

The magic google terms are: 'postfix backup mx'.

If you didn't know the term 'mx', I highly reccomend

	http://www.oreilly.com/catalog/postfix/

...which explains the whole process very clearly.

Oversimplifying, the process is:

	1) List domains you want backup mail service for.
	2) configure your backup mailserver with these domains in:

			relay_recipient_maps

	3) configure your DNS so that your backup mail server has
	   an MX record of with a higher number than your primary

When your first server is returning 400 "temporary failure" errors, the 
stmtp servers trying to connect to it will try your backup.

It is worth noting that when your email server is down, people will keep 
trying to connect to it for 3 days, so you may not need a backup server.