The following warning appears when entering mailbox:
warning: SASL authentication problem: setpass failed for email@example.com: user not found
Such warnings appear when using migrated mail accounts. However mail works correctly even though this warning appears.
Not supported feature
auto_transition is enabled in configuration file /usr/lib64/sasl2/smtpd.conf .
# grep auto_transition /usr/lib64/sasl2/smtpd.conf auto_transition: yes
Actually this warning may be ignored or you can disable
auto_transition feature and the the warning will not appear again
# grep auto_transition /usr/lib64/sasl2/smtpd.conf auto_transition: no