Συντάκτης: Tim Jackson Ημερομηνία: Προς: exim-users Αντικείμενο: Re: [exim] Setting up a fallback e-mail server but maintain normal
operations as well
Hi Sebastian, on Wed, 25 Aug 2004 23:34:33 +0200 you wrote:
> I personally was thinking about this:
> The systems automatically sync DNS data every 15 minutes or so, so why
> not use that domain list.
That's fine.
> Than accept all mail to *@<those domains>.ext, but deny all other
> relaying, and run a spamcheck & virusscan with Exiscan & SpamAssassin.
> If a users account doesn't exist on the target server, the mail will be
> bounced back a few hours/days (or whatever the downtime of the primary
> is) later, as catch all is turned off by standard.
This is a bad idea. Although doing the spam/virus scanning first is good
(assuming you do it at SMTP time), some spam etc. is likely to get
through, and you will end up generating "collateral spam" bounces.
Remember that these days, any time you generate a bounce there is a pretty
good chance that's it's going to either a) go nowhere and end up frozen on
your queue, or b) go to someone who was nothing to do with sending the
original mail. Neither are particularly good; b) is particularly bad.
Basically, as a general rule these days you should avoid generating *any*
bounces whatsoever if you can possibly avoid it.
> Running it from a database would be a bit difficult if I don't want to
> break support for the control panel I use (Direct Admin).
I have no idea how Direct Admin works but if it's from an SQL backend,
couldn't you dump the relevant table, scp it across and reinsert it on the
secondary? A little clumsy, granted, but it then gives you the power to
reject bad recipients on the secondary and avoid generating possible spam
bounces.
