I searched the threads for some similar problem, but couldn't find any.

When trying to send mail using Outlook, the mail basically hangs in the sending folder. Prior to that, a certificate verification is required, but after that, the email doesn't get through. Receiving is ok, IMAP and POP. However, the Test Account Parameter feature (in the Account settings Wizard) does connect to the SMTP and does the full verification process without a single problem...

I'm certain it's a matter of properly configurate the SMTP server settings on the Outlook client (in particular the authentification params), but tried most options available without success. What is strange is that yesterday, it would function properly, with an occasionnal outbound problem like the one descibed here. Now, it's every outbound mail that cannot be processed.

I installed Thunderbird to check if the server config + local and remote firewall rules were ok. Used TLS authentication (if available) for SMTP (SSL doesn't seem to work) and SSL for IMAP and POP: worked like a charm. I cannot replicate this config in Outlook (no TLS on SMTP).

Thanks for your input.