I've OWA with ssl in this server too. The config i've now is:

OWA
IMAP
POP3
SMTP

all with SSL and authentication.

I changed SMTP to anonymous because we are going to move the MX to this server....

I don't think that the bad thing was enable anonymous acces (that was enabled without relay), i think that the bad idea was enable basic auth without SSL... Next week i will test anon an auth w SSL only.