The problem is newsleecher eating all of the concurrent connections limit (50) so avast can't get a look in.
This is what I have from older instances of problems with NewsLeecher:
NewsLeecher - The supersearch uses a protocol other than NNTP on port 119 and that is a problem for the mail scanner. The workaround is the option "Use alt. supersearch port" in NewsLeecher options or to put the address 70.86.176.98 to the AvastUI, Settings, Troubleshooting, Redirect Settings, Mail, ignored addresses. Note: there may have been a change to the IP address, if that one doesn't work, try this one, 174.37.197.132.
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Whilst increasing the current connection limit is an option, I believe that when increased newsleecher will just use more until it reaches the new limit.