Re: [MlMt] SMTP Timeout
Benny and Bill, Thanks. Mr. Cole, you nailed it. I changed from opensmtpd (which I love) to postfix, and I went from an outsourced spam filtering to ASSP, a behemoth of a perl script that is a "transparent" proxy. So far it has done a great job at filtering, but this certainly seems to be their problem. I will do some additional debugging to narrow down which failure it is (I suspect the former), and try to hound them to fix it. Bill, as you seem to be quite knowledgeable in this arena, what is your preferred server side spam handling technique? Off list reply is fine. Thanks, John Grasty On 4 Sep 2014, at 18:22, Bill Cole wrote: On 4 Sep 2014, at 17:03, Benny Kjær Nielsen wrote: On 4 Sep 2014, at 22:18, John Grasty wrote: Every once in a while a message will timeout and not get sent. The activity log shows everything down to the closing . , but the mail server never seems to receive the . It's not a known issue. Could you send me an example of such a log? Off list if you like. This has been seen historically in situations where a stupid "transparent" proxy (notably some versions of Cisco's PIX/ASA "smtp fixup" malware) is mangling SMTP interactions at the application layer. The common error is failure to anticipate the possibility of the terminating . sequence being split between 2 TCP segments and/or read() calls (or their logical equivalents), resulting in the proxy not seeing the whole termination sequence at once. Some SMTP client implementations have adapted to this careless coding by making sure that the message itself is pushed in one segment and the terminating sequence in a segment of its own. This assures that the full sequence isn't split between TCP segments and makes it very unlikely (but not quite impossible) that it will not be returned intact in a single read(). That tactic also slightly mitigates a similar problem when a sending system uses "Path MTU Discovery" and sets the "DONT FRAGMENT" flag on packets, while some intermediary is dropping ICMP "MUST FRAGMENT" replies of some distant device that can't deal with large packets. That problem usually hits every message over 1500 bytes to a particular SMTP server, instead of the "every once in a while" occurrence of the split termination sequence problem. ___ mailmate mailing list mailmate@lists.freron.com http://lists.freron.com/listinfo/mailmate ___ mailmate mailing list mailmate@lists.freron.com http://lists.freron.com/listinfo/mailmate
Re: [MlMt] SMTP Timeout
On 4 Sep 2014, at 17:03, Benny Kjær Nielsen wrote: On 4 Sep 2014, at 22:18, John Grasty wrote: Every once in a while a message will timeout and not get sent. The activity log shows everything down to the closing . , but the mail server never seems to receive the . It's not a known issue. Could you send me an example of such a log? Off list if you like. This has been seen historically in situations where a stupid "transparent" proxy (notably some versions of Cisco's PIX/ASA "smtp fixup" malware) is mangling SMTP interactions at the application layer. The common error is failure to anticipate the possibility of the terminating . sequence being split between 2 TCP segments and/or read() calls (or their logical equivalents), resulting in the proxy not seeing the whole termination sequence at once. Some SMTP client implementations have adapted to this careless coding by making sure that the message itself is pushed in one segment and the terminating sequence in a segment of its own. This assures that the full sequence isn't split between TCP segments and makes it very unlikely (but not quite impossible) that it will not be returned intact in a single read(). That tactic also slightly mitigates a similar problem when a sending system uses "Path MTU Discovery" and sets the "DONT FRAGMENT" flag on packets, while some intermediary is dropping ICMP "MUST FRAGMENT" replies of some distant device that can't deal with large packets. That problem usually hits every message over 1500 bytes to a particular SMTP server, instead of the "every once in a while" occurrence of the split termination sequence problem. ___ mailmate mailing list mailmate@lists.freron.com http://lists.freron.com/listinfo/mailmate
Re: [MlMt] SMTP Timeout
On 4 Sep 2014, at 22:18, John Grasty wrote: Every once in a while a message will timeout and not get sent. The activity log shows everything down to the closing . , but the mail server never seems to receive the . It's not a known issue. Could you send me an example of such a log? Off list if you like. Thanks in advance. -- Benny ___ mailmate mailing list mailmate@lists.freron.com http://lists.freron.com/listinfo/mailmate
[MlMt] SMTP Timeout
Hey Benny and all, I've been using Mailmate for a while. I really love it. I've just made a change to my mail server, and I'm running into an SMTP timeout issue...but only with Mailmate, none of my other clients. Every once in a while a message will timeout and not get sent. The activity log shows everything down to the closing . , but the mail server never seems to receive the . Normally I wouldn't ask, but I've not had a problem with other clients (even when sending the exact same message). Any ideas? Thanks, John Grasty ___ mailmate mailing list mailmate@lists.freron.com http://lists.freron.com/listinfo/mailmate
