Hmmm,
sounds like greylisting. See http://projects.puremagic.com/greylisting/
David M. Shirley wrote:
Thanks.
This gets stranger by the minute. The folks at mmode.com SWEAR they
have made no changes to their sms gateway system and yet tonight:
I rolled back to a prior version of sendmail and found that messages
sent from old (pre-upgrade) sendmail equipped servers are now also
being dropped THE FIRST TIME by mmode.com. If you immediately send it
again, the second message sails right through to my phone.
I get the same behavior from old sendmail equipped servers that were
functioning fine earlier today and have never been upgraded.
I took a server that:
can't get any messages through to mmode.com with the new sendmail
and has it's first message to mmode.com lost using the old sendmail
switched to using postfix and all messages now sail right through each
and every time.
In all three cases, the mmode.com server accepts the messages for
delivery in exactly the same way as I have reported earlier in this
thread.
It's pretty clear now that this is purely an mmode.com problem but
they seem unable to locate anything. If anyone has some insight, I'd
love to be able to tell them, "Hey did you check this...?"
This bit about always losing the first message sounds a bit like a
botched attempt at greylisting but I don't understand how it only
occurs with connections from sendmail mtas and not others like qmail,
postfix and exim.... Indeed messages from any of these other mtas are
accepted my mmode.com the first time, every time.
David Shirley
http://www.webquarry.com
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