Re: sendmail AUTH

Wolfgang Agnes <wagnes@jemoni.to> writes:

Thanks!  I don't know how to investigate it further after I type
STARTTLS.  I believe that after I issue STARTTLS, I'd have to speak the
TLS protocol, which I don't know how.

You can have openssl connect and issue the STARTTLS, and then continue
with TLS.  Like so:

bjorn@miraculix:~$ openssl s_client -connect canardo:25 -starttls smtp -quiet
Can't use SSL_get_servername
depth=2 C = US, O = Internet Security Research Group, CN = ISRG Root X1
verify return:1
depth=1 C = US, O = Let's Encrypt, CN = R11
verify return:1
depth=0 CN = canardo.mork.no
verify return:1
250 HELP
ehlo du
250-canardo.dyn.mork.no Hello [IPv6:2a01:799:10de:2e0a:149a:2079:3a3a:3457], pleased to meet you
250-ENHANCEDSTATUSCODES
250-PIPELINING
250-EXPN
250-VERB
250-8BITMIME
250-SIZE
250-DSN
250-ETRN
250-AUTH PLAIN LOGIN
250-DELIVERBY
250 HELP
quit
221 2.0.0 canardo.dyn.mork.no closing connection


Drop the "-quiet" option to get more details about the TLS negotiation,
or add other options.  You can also send client certificate if you want,
using -key and -cert. And there are plenty of other options as usual
with openssl :-)

See the openssl s_client manual page for more details.


Bjørn