On Nov 9, 2006, at 11:37 AM, Jakob Hirsch wrote:
> Quoting Marc Perkel:
>
>> I was just wondering if there were known MTAs that don't try all MX
>> records but only the lowest? Is this something that's common?
>
> I guess by "lowest", you mean the lowest preference number, i.e. the
> highest priority.
>
> qmail ist known for strange behaviour. AFAIR, it does only fall
> back to
> lower priority MXs after a connection failure, but not if the
> connection was established and a smtp error response was given.
> I'm not astonished. qmail has so many flaws that somebody even
> bothered
> to set up a web page documenting it... ah, here it is:
> http://home.pages.de/~mandree/qmail-bugs.html
>
> quote: "... that qmail would never try any other MX than the first it
> connects to, even if that MX does not reply with a 220 greeting. When
> the server replies with e. g. a 554 greeting, qmail disconnects and
> later retries the same server again, ignoring the fact that 554 is a
> permanent error."
Even worse, Mdaemon 8's default behavior is to try the next MX when
presented with 5xx response.
You can turn on the "feature" to respect this, but only in response
to a RCPT TO command.
If you get it in response to DATA (like when you are trying to send a
message too big), it does not bounce but tries the next MX. One
weekend, a MDaemon server of our customers pounded some poor sod's T1
line all weekend trying to deliver some messages that were too big.
I gave the AltN techs an earful when calling on a related issue.
Brian
