Hi Mailop, We run our listening mail servers with a maximum header size limit of 32768 (Sendmail's default).
We've found at least one "legitimate" sender whose headers are far bigger than that, and the reason for this isn't a very long path :-) it's all the "x-microsoft-exchange-diagnostics-untrusted" multiline headers being dumped in there by one of the O365 tenancies outside our control. Obviously we're asking the sender to see if they really need to have all that header data added, but in the meantime I'd like to ask this community whether you see that 32KB max header size as a sensible limit in today's conditions? -- 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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