well...I may have fixed mine. I kind of remember getting an error message from Avast something about disabling SSL/TLS in my mail program so that it could take care of scanning the mail stream. So I had gone into eM Client to the Tools, Accounts and then under each of my 2 accounts I had checked "Don't use secure connection" for both SMTP tab and POP3 tab.
So I went back in and changed those settings so that now I have my SMTP settings set to "Use SSL/TLS on special port (legacy)" with port 465. My POP3 settings are now "Use SSL/TSL if available" and port is set to 110. (Note your mail server may be different...if these don't work use the Diagnostics tab and click on Fix. Hopefully it can find you the right settings for your mail server. I am not using Optimum/Bresnan mail)
In Avast! Free go to user interface, click on Real Time Shields, Select Mail Shield, click on Expert Settings, then select the SSL Accounts tab. I think Avast! detects and makes these entries automatically (or maybe I entered them once but I don't think so). I have 2 listings: Host Name for both is westdc.net and then the 1st is POP3, 110, TLS and the other is SMTP, 465, SSL.
I am no longer getting the popup message upon launching...however I then changed back to what I thought were my old settings and I did not get them either.

Hmmmm

So maybe I didn't put them back quite right or maybe something else is at work. I'll relaunch tomorrow and see if all is still good.
Easy enough to test...so maybe give this a try and see if it works for you. Good luck. Let me know how it goes. Thanks.