I can't send email from outlook 2013, installed on windows 8.1

[Leegethas]

I have two cases where a client uses outlook 2013, installed on windows 8. No matter what I try, I can't get outlook to send email through my plesk-server. I keep getting the error: your server does not support the connection encryption type you have specified.

This problem only seems to occur with the outlook 2013 + windows 8 combination and it is driving me nuts! I can configure Thunderbird without any problems what-so-ever. And when sending mails through a non-plesk (but also Postfix based) server, it works just fine.

Does someone know why I get this error and how to fix this?

 

[abdi]

Have you tried setting outlook to use TLS (or AUTO) as an encryption method ...

 

[Leegethas]

Yes. I tried port 465 and port 587. Both SSL, TLS and auto. Nothing works.