[Mimedefang] What is the order of things that occur

Alan Premselaar alien at 12inch.com
Wed Jul 12 09:47:34 EDT 2006


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Steve,

Steve Campbell wrote:
> Jan-Pieter,
> 
> Thanks and wow!
> 
> Quoting Jan-Pieter Cornet <johnpc at xs4all.nl>:
> 
>> On Tue, Jul 11, 2006 at 04:00:05PM -0400, Steve Campbell wrote:
>>>> In the current internet, there isn't any point in having a secondary
>>>> MX just for the purpose of fallback, if your primary server is mostly
>>>> up.
> 
> The servers that I am running these on are pretty tough Dell servers (real
> server class) with SCSI Raid and dual Power and all. Of course, I realize these
> can break as easily at the XTs I run our web sites on. (smily thing here)
>  
>> No, the secondary would tempfail too, so you end up NOT accepting the
>> email on the secondary. Try it.

for the most part this is true, however you can easily code your
filter_recipient() subroutine to accept and queue the mail if the
primary server doesn't respond.  there are obvious downsides to doing
this (like having to accept mail for unknown users and then probably
generating DSNs for them) but it can be done.

I have something like this in my backup MX's filter:

        my ($answer,$msg) = md_check_against_smtp_server($from,$to,
"backup_mx_hostname", $check_mail_server);
        $answer = 'CONTINUE' if ($answer eq 'TEMPFAIL');

        return($answer,$msg) if ($answer ne 'CONTINUE');

after this I do greylisting routines, you could just as easily just
return ($answer,$msg) there w/o the conditional and that would queue up
the mail.


...lots of snippage...

I tend to agree that in today's internet environment, there's not nearly
as much merit to having a backup MX as there was in the days of UUNET
and periodic dialup mail transports, but it certainly gives the PHB the
warm fuzzies. (I'm kind of stuck in the same boat in that respect)

anyways, hope this helps.

Alan
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