Ok, I looked at that and appears it sends me to this solution:
Outgoing SMTP Authentication - Zimbra :: Wiki
Our ISP says just send mail out on port 587 as they dont block that.
"Some ISP's SMTP servers do not implement TLS properly on port 465 (AT&T Yahoo DSL in particular); mail clients handle this when making an SSL connection, however Postfix loses the server connection in this case. Port 587, the standard secondary SSL SMTP port, does work properly with TLS.
The proper commands for AT&T DSL customers in the above setup are:
Change:
zmprov ms server.domain.com zimbraMtaRelayHost external.relay.com:#
To:
zmprov ms server.domain.com zimbraMtaRelayHost smtp.att.yahoo.com:587
And add:
postconf -e smtp_sasl_mechanism_filter=plain,login
postconf -e smtp_sasl_security_options=noanonymous
postconf -e smtp_tls_security_level=may
" of course adding MY ISP ? Thanks.
The problem is that I am getting: relay = outgoing.verizon.net, delay482 status=deferred (SASL authentication failed; (Not Authorized to login as specified user)