[cobalt-users] How can I forward all mail for a domain to another mail server

[Clive Harper <CHarper@xxxxxxxxxxxx>]

I have looked through the archives but still cannot find
an answer to this, can someone please point me in the right
direction as I am sure this has been discussed before.

We have a customer who is running their own Linux mail
server, they have a leased line connection so the MX record
points directly to their mail server.

They are constantly reporting that they are losing mail from
their server, either due to network problems or the mail
server itself, anyway they have asked if we could act as a
mail host for them and provide a cache of recent mails just
in case some go missing at their mail server.

How can we do this on a RAQ4, I can get the MX record changed
to point to a site on the RAQ but how can I pass this
mail on to their mail server keeping the username intact. (I
do not want to forward all mails to a single recipient). I
thought about using SMTP relaying but cannot find any info
about how to set this up the way we want it.

Secondly how can I keep a copy of all the mails sent to this
domain for appx 7 days before deleting them?

Any help would be appreciated.

--
Clive Harper