[CentOS] company exchange server & exim best practices.

Rudi Ahlers rudiahlers at gmail.com
Fri Apr 3 10:13:50 UTC 2009


On Fri, Apr 3, 2009 at 10:09 AM, Michel van Deventer
<michel at van.deventer.cx> wrote:
> Hi,
>
> my solution to this kind of problem is the following :
> Set up a relay mailserver (in my case Postfix) which accepts mail (and
> has the MX record for the domain) for the domain but has no mailboxes.
> Postfix takes care of spamblocking (dnsbl and spamfilter ). In Postfix I
> use a transport table to relay the mail to the Exchange/Whatever
> mailserver, that can also be on a nonstandard port (in my case port
> 2525).
> Delivering to a dyndns host is really easy, Dyndns uses a short ttl for
> the hostname (something like 3 minutes ?). I set up a nameserver record
> which let a 'fixed' name (like mail.domain.nl) point to the dyndns name
> using CNAME.
> mail.domain.nl. IN CNAME mailhost.dyndns.org
>
> Sending the mail to the dyndns hostname directly without the nameserver
> trick is also possible.
>
> Using a non-standard port is to bypass SMTP limits from the provider and
> to make (almost) sure your mail doesn't get delivered to a mailserver of
> someone else ;)
>
>        Regards,
>
>        Michel
>
>
> On Fri, 2009-04-03 at 09:40 +0200, Rudi Ahlers wrote:
>> Hi all,
>>
>> I hope this isn't too OT, but since I use a CentOS5.2 + Exim mail
>> server (which is hosted in one of our data centres) I don't think it
>> should be.
>>
>> On of our clients use an MS Exchange 2003 SBS server, with exchange
>> for their internal email. We provide them with a domain, ADSL (which
>> uses dynamic DNS) and POP3 email. They don't have an spam filter
>> program on the exchange server itself due to costs, so I have setup
>> each user on the Exim server, which runs ASSPX for anti-virus / spam
>> filter / etc. Then I setup the SBS 2003 server to pull the email via
>> POP3, but this doesn't seem to work too well, cause the exchange
>> server doesn't always download the POP3 email, and then the users
>> often sit without email until I go there to manually download the mail
>> again.
>>
>> I have tried changing the MX record to point to their DynDNS address,
>> and it works well, but then they get a lot of spam. And the cost of a
>> server-side spam solution is just too expensive, and they also pay for
>> the bandwidth uses when spam comes in. So, I moved their MX record
>> back to the Linux server. But now I sit with the problem of the POP3
>> connector failing from time to time.
>>
>> So, I would like to know, is there a way to "push" (not forward) mail
>> from the Linux server, after it has arrived and spam been blocked, to
>> another domain, but with the same email address? i.e. the domain in
>> question is attorneys.co.za and I've setup attorneys.dyndns.net as the
>> dynamic domain, but the exchange serves email for attorneys.co.za
>> Forwarding email doesn't work, since there's no such user as
>> bob at attorneys.dyndns.net, but rather bob at attorneys.co.za.
>>
>
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Thanx Michel, but how todo this on Exim? :) lemme see if I can find
similar scenarios for Exim, now that I know what to look for.

-- 

Kind Regards
Rudi Ahlers


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