email inactive

Installed Avast Premier and for last 24 hours no email has been delivered via Eudora or Thunderbird.
When check my server, latest emails are there.
What is preventing my email programs from delivering this mail? Something in Avast I suspect.
Also, must I click on Avast icon on desktop to have it running in Taskbar or does it run in background anyway?
Thanks for any info.

What exact version of avast ?
What OS/SP ?
Is there any other security (related) software installed ? (or was there)
Did you exported the avast certificate and imported it in your mail clients ?

It says Avast Premier 2015 (latest one).
OS is Windows 8.1
Brighthouse networks is SP.
No certificates involved; no importing done.