zmprov gs myhost.com | grep zimbraMtaAuth
zmprov gs myhost.com | grep zimbraMailMode
zmprov gs myhost.com | grep zimbraMailPort
zmprov gs myhost.com | grep zimbraMailSSLPort
I did zmcontrol stop/start earlier to see if it would crank back up...would these commands give useful output when the mailbox and mta have failed ? If so I will run them if/when it happens again.[/QUOTE]
You've hit the bug - notice that your auth URL is https://..., but your mail mode is http - the workaround is to either reset your mtaAuthHost (to the value it's currently set to) or to change your mail mode (depending on whether the mail mode is correct for your purposes).
zmprov ms myhost.com zimbraMtaAuthHost myhost.com
zmtlsctl https (or mixed)