SMTP <https://datatracker.ietf.org/doc/html/rfc2821#section-4.1.1.4 https://datatracker.ietf.org/doc/html/rfc2821#section-4.1.1....> is pretty clear that the me

SMTP <https://datatracker.ietf.org/doc/html/rfc2821#section-4.1.1.4 https://datatracker.ietf.org/doc/html/rfc2821#section-4.1.1....> is pretty clear that the message termination sequence is CR LF . CR LF, not LF . LF, and disagreements in this spot are known to cause problems (include undesirable message injection). But then enough alternative implementations that recognize LF . LF as well are out there, so maybe the original SMTP rules do not matter anymore.