Hello:
I’m new to Avast and I have a problem with the mail shield.
I have all my accounts configured on Avast but my M2 (opera’s mail client) is unable to send mail when Avast shield is enabled to check for outgoing messages. Only disabling the shield allows me to send mail.
The problem is mostly with gmail’s imap account.
Any thoughts? I don’t like disabling shields in order to make things work.
Having exact same problem here. Any help would be awesome!! 
In the avast shield, it will show some accounts with SSL, have you tried deleting those and then opening / closing your mail program so avast detect them again
avast! 5.x: The Mail Shield may not scan some e-mails
https://support.avast.com/index.php?_m=knowledgebase&_a=viewarticle&kbarticleid=458&nav=0,64
INFO: Gamil is scanning all mail accounts in/out on there mailserver with two virus scanners McAfee and Authentium so you are still protected