- Update to version sendmail 8.18.1 2024/01/31
* sendmail is now stricter in following the RFCs and rejects
some invalid input with respect to line endings
and pipelining:
- Prevent transaction stuffing by ensuring SMTP clients
wait for the HELO/EHLO and DATA response before sending
further SMTP commands. This can be disabled using
the new srv_features option 'F'. Issue reported by
Yepeng Pan and Christian Rossow from CISPA Helmholtz
Center for Information Security.
- 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.
* Full DANE support is available if OpenSSL versions 1.1.1 or 3.x
are used, i.e., TLSA RR 2-x-y and 3-x-y are supported
as required by RFC 7672.
* OpenSSL version 3.0.x is supported. Note: OpenSSL 3 loads by
default an openssl.cnf file from a location specified
in the library which may cause unwanted behaviour
in sendmail. Hence sendmail sets the environment
variable OPENSSL_CONF to /etc/mail/sendmail.ossl
to override the default. The file name can be