Sendmail and backup MX

[Scott Silva]

John Rudd spake the following on 9/26/2005 4:05 PM:
> On Sep 26, 2005, at 15:41, Scott Silva wrote:
> 
>> John Rudd spake the following on 9/26/2005 2:37 PM:
>>
>>> On Sep 26, 2005, at 12:13, Scott Silva wrote:
>>>
>>>> Not a MailScanner issue, but ...
>>>> Does anybody have any simple solutions for sendmail that only lets the
>>>> backup MX accept mail when the primary is down?
>>>> I don't want to re-invent the wheel if someone already has a working
>>>> solution.
>>>>
>>>
>>> Get mimedefang.  Run it on your backup.  www.mimedefang.org
>>>
>>>
>>> There's a function it has called "filter_recipient" which you have to
>>> write (in /etc/mail/mimedefang-filter), and which you have to turn on in
>>> the startup script.  Here's what I would suggest:
>>>
>>>
>>> sub filter_recipient {
>>>    my ($recip, $sender, $ip, $host, $first, $helo, $rcpt_mailer,
>>>        $rcpt_host, $rcpt_addr) = @_;
>>>    my ($type, $msg);
>>>
>>>    # if the recipient is in the domain I secondary
>>>    if ($recip =~ /\@primary\.domain\.name\b/i) {
>>>
>>>       # verify a known recipient on the primary
>>>       ($type, $msg) = md_check_against_smtp_server($sender,
>>>                         $recip,                # known recipient
>>>                         "secondary.host.name", # your backup/MX server
>>>                         "primary.host.name");  # the primary mail server
>>>
>>>       if ($type  eq "REJECT") {
>>>          # the recipient doesn't exist, hard reject even if
>>>          # the primary is up
>>>          return ('REJECT', "Unknown Recipient");
>>>          }
>>>       elsif ($type eq "CONTINUE") {
>>>          # if you can verify it, then the primary is up
>>>          # TEMPFAIL (or REJECT) the message
>>>          return ('TEMPFAIL', "Only call me when the primary is down");
>>>          }
>>>       else {
>>>          # else, primary is down or having problems
>>>          return ('CONTINUE', "OK");
>>>          }
>>>       }
>>>    }
>>>
>> I'll look at this this week!
>> Looks like it will do the equivalent of milter-ahead also.
>> Thanks!!
>>
> 
> Yes, you can also use this as a means of replacing milter-ahead.  You
> can also implement greylisting with it.
> 
> Though, be careful.  It will detect any virus scanners you have
> installed, and the default mimedefang-filter will try to run them.  That
> can put a lot of extra work on your machine, since you'll be doing it
> both in mimedefang and mailscanner.  So, when you do the "configure" in
> mimedefang, you should look and see  what you need to do to turn off
> whatever virus scanners you're using.
> 
> (there's also a way to turn them off in mimedefang-filter, OR you can
> simple comment out the parts of "filter_begin", "filter",
> "filter_multipart", and "filter_end" which duplicate mailscanner
> functionality; virus scanning is in filter_begin, attachment
> filename/etc. checking is in filter and filter_multipart, and spam
> assassin is in filter_end)
> 
I think I just want to use the above, and let MailScanner do the rest. I
have a copy of the mimedefang howto in my hands right now.


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