I am recording this for anyone with the same message in the admin panel.
No emails were being received on one of my 3 mail-in-a-boxes. The admin panel showed that Spamassassin was not running. In /var/log/mail.log I found:
postfix/smtpd[14805]: warning: restriction `reject_authenticated_sender_login_mismatch’ ignored: no SASL support
A server reboot changed nothing but then a restart of sasl fixed the problem:
/etc/init.d/saslauthd start
This never happened before to me but was just 4 days after upgrading to v0.48. Maybe a coincidence?