ST> Date: Wed, 12 Apr 2006 18:56:44 -0700 (PDT) ST> From: Steve Thomas ST> If you accept the message, you can presumably deliver it. In this Possibly. However, insufficient storage is not the only cause of 4xx status. ST> day and age, anyone accepting mail for a domain without first ST> checking the RCPT TO - even (especially?) on a backup MX - should ST> have their head examined. Especially. ST> IN the event that the RCPT TO is valid but the message truly can't ST> be delivered for some other reason, you should bounce the message ST> and fix the problem. *Iff* the bounce can be sent to the correct location. That's a big iff these days. ST> My point was that when it comes to spam, it should either be rejected ST> inline or delivered. That's ideal. I can think of several realistic conditions where a message could be queued but not validated until later. I'm simply stating that { accepted | pending | refused } is a reasonable set of responses. From an end-to-end perspective, SMTP transactions are asynchronous and not guaranteed, anyway. You're advocating run-to-completion. I'm suggesting an asynchronous realtime system instead. Polls could be coalesced. Note also the implications of polling for message status: Eliminate bounces. Want to know if a message went through? Poll. Receive bounce inline if appropriate. That seems better than the current push-based crapshoot. Want to confirm that a user has retrieved a message? Now possible at the MX level. Want to confirm receipt by the server without divulging if the user has retrieved the message? Return a status code indicating such. Frankly, I'd go for pull-based response codes just to be rid of backscatter. The rest is gravy. Eddy -- Everquick Internet - http://www.everquick.net/ A division of Brotsman & Dreger, Inc. - http://www.brotsman.com/ Bandwidth, consulting, e-commerce, hosting, and network building Phone: +1 785 865 5885 Lawrence and [inter]national Phone: +1 316 794 8922 Wichita ________________________________________________________________________ DO NOT send mail to the following addresses: davidc@brics.com -*- jfconmaapaq@intc.net -*- sam@everquick.net Sending mail to spambait addresses is a great way to get blocked. Ditto for broken OOO autoresponders and foolish AV software backscatter.