High-availability on a mail relay

[Manel Ventura]

Hi,

I've got a mail relay on a SuSE Linux. Now I'm trying to figure out how to add a standby server to obtain a high-availability service. Has anyone an idea to implement this?

[Ralf Hildebrandt · Accepted solution]

a) make sure it uses Postfix instead of sendmail. sendmail is a security desaster, and postfix outperforms it. Also, it's more secure.
b) Simply clone the box. For incoming mail for your domain specify two MX records, one pointing to each box. If one is down, the other box will be used
c) for outgoing mail simply use internal DNS to alias the two boxes to a common name (e.g. smtp.yourdomain.com). Should one box fail to work, the other will be used

d) Don't use SUSE. Security is bad, the system suffers from too much bloat. Debian is leaner.

[Bill Thorsteinson]

Choosing Linux (UNIX in general) gets you 99% of the
way there.

Step 1: Install a UPS. Power is one of the few things
that I have found can reliably bring down Linux.

Debian is very solid and easy to update. exim is the
default MTA and is very stable. As far as I have been
able to discover it is also very secure.

Step 2: Check the relevant chapters in the
UNIX System Administration Handbook.
I think they cover a very solid setup. I don't have
a copy here so I can't verify.

Step 3: Determine your strategy for fall-back. You can use dual servers as Ralf described, or a fallback server.
Your incoming servers need to have some shared alias
files. Consider using rsync to mantain syncronization.
Use different servers for incoming and outgoing traffic.

If you choose to use dual servers you can use a single
MX and map the ips of both servers to the same name.

If you choose a fallback server then set-up the MX
records accordingly.

[Manel Ventura]

Guys,

I really appreciate your help. I 'll choose the best choice.

Manel.