Quoting Jim Cheetham (2016-11-01 16:02:29) > We run our listening mail servers with a maximum header size limit of 32768 > (Sendmail's default).
Thanks to the responders showing different limits, reminding me to RTFM and check the default configs of some other products :-) In size order ... Sendmail: 32KB Postfix: 100KB Cisco ASA/ESA: 1000 lines Exchange 2016: 256KB Exim: 1MB Google: 1MB qmail: memory Checking one set of servers here, out of ~100,000 inbound messages, we saw 14 rejected as "headers too large", the sources were: 1 from Yahoo! 2 from Google 5 from Outlook.com 6 from an Azure host (didn't look like any email we wanted) On the face of that, I'm going to recommend raising our MaxHeadersLength from 32768 to 262114 in the current production servers, and to 1MB for the next iteration of servers. -- Jim Cheetham, Information Security, University of Otago, Dunedin, N.Z. ✉ jim.cheet...@otago.ac.nz ☏ +64 3 470 4670 ☏ m +64 21 279 4670 ⚷ OpenPGP: B50F BE3B D49B 3A8A 9CC3 8966 9374 82CD C982 0605
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