Secondary mail server

I have qmail with vpopmail set up for a company mail server (fairly
light duty).

I'd like to set up a separate machine as the backup mail server for
the domain, where the primary would use fetchmail to retrieve any mail
caught by the secondary.

I was wondering if there are any canned or semi-canned ways to do
this, since I'd like to avoid having to duplicate the vpopmail
configuration (and updating it to match the primary server).

Ideally, it would be something that would act something like a caching
mail server for the domain. That is, it accepts all messages for the
configured domain, then tries to deliver them all to the primary like
a normal mail queue, leaving the primary to deal with the validity of
destination addresses.

Any hints on the best way to proceed?
--
- Mike

Ignore the Python in me to send e-mail.

On Tue, 07 Feb 2006, in the Usenet newsgroup comp.os.linux.networking, in
article <(E-Mail Removed)>, Mike Ruskai wrote:

>I'd like to set up a separate machine as the backup mail server for
>the domain, where the primary would use fetchmail to retrieve any mail
>caught by the secondary.

I don't know about qmail, but normally a secondary forwards mail to the
primary using SMTP, not POP or IMAP. Are you sure you need to go this
way?

>Ideally, it would be something that would act something like a caching
>mail server for the domain. That is, it accepts all messages for the
>configured domain, then tries to deliver them all to the primary like
>a normal mail queue, leaving the primary to deal with the validity of
>destination addresses.

That's the normal mechanism, which is why I don't understand why you
are using a local delivery protocol like POP or IMAP. One finger-wag
caution - be careful on setting this up. The secondary should have the
same knowledge of valid usernames as the primary, so that it can reject
invalid usernames at the "RCPT TO" dialog with the originating mail
server (see RFC0821 and RFC2821). Don't plan on trying to bounce mail
on the primary that you've already accepted for delivery by the
secondary, or you WILL find yourself on mail block/black lists because
you try to bounce spam that arrived with forged headers.

Old guy

Mike Ruskai <(E-Mail Removed)> écrivait
news:(E-Mail Removed):

> I'd like to set up a separate machine as the backup mail server for
> the domain, where the primary would use fetchmail to retrieve any mail
> caught by the secondary.
>
> I was wondering if there are any canned or semi-canned ways to do
> this, since I'd like to avoid having to duplicate the vpopmail
> configuration (and updating it to match the primary server).
>
> Ideally, it would be something that would act something like a caching
> mail server for the domain. That is, it accepts all messages for the
> configured domain, then tries to deliver them all to the primary like
> a normal mail queue, leaving the primary to deal with the validity of
> destination addresses.

That's exactly as mail servers runs :

- the domain DNS set two MX record with differents preferences (the
number before the hostname in the dns zone file).

then

- "outsider" mail client or smtp relay send mail for your domain to the
lowest preference server, and if this one don't answer the mail is send
to the lowest available mail server

- your mail servers check themselves if they are the lowest preferenced
one. If none they try to send the mail to the lowest one.

So, for the cache mail server, you "just" need to set it to accept mail
for the domain and set dns zone with a upper preference than the
"primary" mail server.

You may decide to install a "simple" postfix or exim mail server for the
second one.


Regards