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Delay Filter [message #1285] Thu, 27 October 2005 23:00
Messages: 23
Registered: March 2005
Junior Member
I took my first stab at a 30 second "Delay Filter" yesterday. For the next hour, the "Mail Storage" filter (first filter) saved all messages correctly, but the "Delay Filter" (30 seconds delay, 2nd filter) caused the e-mail server to deliver blank subject and text messages to the end user. Was the e-mail server giving up after 30 seconds?
Re: Delay Filter [message #1286 is a reply to message #1285] Fri, 28 October 2005 11:30 Go to previous message
Messages: 925
Registered: April 2004
Senior Member
A scenario like you described requires both the the sending and receiving MTAs not to comply to the SMTP standard:

- a sending MTA must wait a reasonable time (about 5-10 minutes) for the receiving MTAs acknowledgement before disconnecting. That's why the delay filter works, usually only Spammers use short timeouts in the range of a few seconds only.

- if the sending MTA aborts a message transmission (that is what happens if the sending MTA disconnects instead of waiting for the acknowledgement), the receiving MTA isn't supposed to deliver anything to the user, not even an empty message.

If you are interested in this matter please take a look at RFC-2821 (
NoSpamToday! delays the DATA command to the outgoing server until it is sure that the message will be delivered. If the sending MTA disconnects during the delay time, the outgoing server will never see the DATA command. I don't believe there is a mail server software that creates an empty message if no message was delivered at all.

Post Edited (10-28-05 11:32)

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