UPDATE May 28
Vlad doesn't see an issue sending mail with 8.1 on his server, so he can't reproduce.
Since email works on other servers, we're leaning towards some issue with Upcloud.
We need anyone who has UPCLOUD WITH WINDOWS to do an email test using the demo CRM app. 5 minutes is all thats needed.
NOTE:
You have to modify the CRM app to allow access to System Settings to enter OutGoing Email settings. I add a menu to Top Bar.
You also have to modify the SystemSettings FORM to include the TLS field (if needed).
In Runtime, enter Email Settings, then go to Customers tab, expand 1st entry, change email to your email.
Then [New Email] button top/right of her form.
Just enter subject, message, and duration and SAVE.
Spinner should barely appear ( mine stays on for 10 seconds ).
Also check Server Output window - should see a line confirming "Email sent to xxx@xxx".
Did you see Java errors for Incorrect Header Check?
(UPDATE: Vlad has since said the Incorrect Header Check is benign, and can be ignored.)
This issue wouldn't show up if you're using Mandrill, Gmail, etc.
Simple test as describe here: https://www.awareim.com/forum/posting.php?mode=reply&f=1&t=10345#pr47287
THANKS!!!