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FYI, Sendmail accepts LF without CR, but Exchange doesn't.
by chasil 2y ago
FYI, Sendmail accepts LF without CR, but Exchange doesn't.
- 9dev 2y ago…how very in character for each of them!
- isThereClarity 2y agosendmail 8.18.1 includes patches to correct this behaviour (and options to turn it back on) due to its role in SMTP smuggling, CVE-2023-51765. See https://ftp.sendmail.org/RELEASE_NOTES https://ftp.sendmail.org/RELEASE_NOTES sendmail is now stricter in following the RFCs and rejects some invalid input with respect to line endings and pipelining: ...snip... - Accept only CRLF . CRLF as end of an SMTP message as required by the RFCs, which can disabled by the new srv_features option 'O'. - Do not accept a CR or LF except in the combination CRLF (as required by the RFCs). These checks can be disabled by the new srv_features options 'U' and 'G', respectively. In this case it is suggested to use 'u2' and 'g2' instead so the server replaces offending bare CR or bare LF with a space. It is recommended to only turn these protections off for trusted networks due to the potential for abuse.