I followed the procedure to Integrate Amazon SES with Sendmail in Ubuntu as given in the guide. The error log at
/var/log/mail.logshows that “AUTH=client, available mechanisms do not fulfill requirements” and “Temporary AUTH failure“. However, it also showed “Message accepted for delivery“.
Apr 26 19:35:46 ABC sm-mta[24892]: 33QE5jZl024892: AUTH=client, available mechanisms do not fulfill requirements
Apr 26 19:35:46 ABC sm-mta[24892]: AUTH=client, relay=email-smtp.ap-south-1.amazonaws.com., temporary failure, connection abort
Apr 26 19:35:46 ABC sm-mta[24892]: 33QE5jZl024892: to=<pqr@gmail.com>, delay=00:00:01, xdelay=00:00:01, mailer=relay, pri=30278, relay=email-smtp.ap-south-1.amazonaws.com. [15.206.39.42], dsn=4.0.0, stat=Deferred: Temporary AUTH failure
Apr 26 19:35:46 ABC sendmail[24877]: 33QE5aBZ024877: to=pqr@gmail.com, ctladdr=admin@demo.com (0/0), delay=00:00:10, xdelay=00:00:01, mailer=relay, pri=30010, relay=[127.0.0.1] [127.0.0.1], dsn=2.0.0, stat=Sent (33QE5jZl024892 Message accepted for delivery)
As explained in stackoverflow, installing the sasl2-bin and libsasl2-modules solved the problem.