Please also see #16064, the sendmail side of the story.
While building cyrus-sasl, CRAM-MD5 is explicitly disabled. Is there a
specific reason for this?
I was wondering because I saw the list of SMTP authentication methods
different MUA's support, and DIGEST-MD5 was rare; on the other hand,
CRAM-MD5 seemed to be much widely supported:
Will be fixed in cyrus-sasl-1.5.24-4.