[lug] [ot] MX backup partners

[David Anselmi]

Daniel Webb wrote:
> I'm looking for people running stable mail servers to allow me and a
> friend to use them as a backup MX server.  We already have each other as
> backups, but we are in the same wing of a building, and the power
> sometimes goes down for the whole wing.  We could of course do the same
> for you if desired.

Do you need another backup?  Does mail actually bounce when your servers 
are down?  I'm not saying you don't, just trying to understand what 
you're experiencing.

Presumably your servers aren't down for days at a time.  So when they 
are down mail delivery should be retried and get through when they come 
back up.  I've gotten messages that say "couldn't deliver in 4 hours, 
I'll keep trying for 5 days" for mail I've sent.

Let's see what my exim setup says...  It will try for up to 4 days.

All the backups do is accept mail and then pass it on to the primary, right?

So assuming most MTAs try to deliver for days and your primary server is 
mostly up, adding backups may not do much.

On the other hand, some DNS failures seem to bounce mail immediately 
while some don't.  So if your mail does bounce when your server is down 
maybe you need more reliable DNS rather than more reliable mail servers.

Dave