no problems with mails at all (except the scanning is missing).
The avst mail service is running manually with windows" .
Sorry, the question could be stupid but, did you set avast for scanning the inbound (pop3) and outbound (smtp) mail?
Internet Mail provider > Customize and both POP3 and SMTP tabs.
Again, the email clients use
Internet Mail (pop3/smtp protocols): Outlook Express, Thunderbird, Pegasus Mail, IncrediMail... On other hand, MS Outlook (not the Express) uses the Outlook/Exchange plugin from avast.