Hello.
As a presentation, I am very amateur at all this despite I could manage to have my site running over Hestia. Said so…
Months ago I tried to setup mail in my Hestia server with no luck. From then on I relied on a Gmail account. It’s ok, I could cope with it. The weird thing is yesterday I started receiving mails from my Drupal installation what means the Hestia upgrade changed something that made sending mail from server work (with my actual configuration).
To me it is good news. Very good ones, actually. As soon as I have time I’ll check the panel and try to fine tune it. An excuse to say THANK YOU for such a great product you develop. Always issues and complaints s not nice at all. 
Have a nice day!