howto setup a backup mx server?

My friend has a mail server, however, sometimes his machine is not online and would like me to be a backup mail server for him.  I know how to setup my machine as backup in the DNS entry but what program is good to handle backup mail servers?

My machine is Mandrake 8.2
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samriConnect With a Mentor Commented:

Basically you would need to have the MX entries for the domain to point to your mail server (I would presume it's sendmail).  Make sure the MX preference is lower (higher number).  In this case, any mail will get sent to the default server (your friend's email server), in case that the server is not reacheable, then your server will be contacted.

Take a look at Virtual Hosting page on Sendmail's website for more detail on how to get it done.
Basically, what needs to be done on your sendmail is to enable add yourfriends domain to /etc/mail/, configure the virtusertable to have the entry

With this approach your server will be accepting mail for, and with the virtualuser mapping, an attempt is made by your server to send the mail to the actual recipient (  However, since the server is not reachable, the mail will spool in your machine.  Another attempt will be made in the future based on your sendmail setting (4hrs, 1 day, etc .etc).

Depending on the volume of mail (# of mails, and size), you would need to have an ample space in /var/spool/mqueue.

calvinrsmithAuthor Commented:
Sendmail looks to complicated to setup for such a simple task, is there an easier program?
some people find qmail or postfix "easier" (whateverthismeans:)
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ahoffman is correct.  Easy/Complicated is really depending on how often you try.  I would say sendmail is pretty straightforward, somebody else might say qmail or postfix (*grin* at ahoffman).

Perhaps you might take a look at other alternative - postfix or qmail, and decide.  Then maybe we all could elaborate on that.

To make like a bit easier (I hope), grab yourself a copy of Webmin ( and try the web based admin for Sendmail, or Postfix, (and I think Qmail too).  Still some understanding of virtual hosting is required.

Uhm, Since you have a Mandrake8.2, you probably already installed postfix Calvin.
Webmin is included in the distro too, so you should just have to install it;).

-- Glenn
So (10 months, more or less, later) is it time to "elaborate" now, or did you get anything set up?

-- Glenn (Who is going through the "real-old-unlocked-questions" he has commented in)
calvinrsmithAuthor Commented:
forgot about this,  i eventually found a copy of eXtremail and set it up.
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