Why?
You can configure your email account manually. Your configuration must be:

SMTP server: 127.0.0.1
POP server: 127.0.0.1
account login: user name#isp name
Note: # and not @

smtp authentication on
user id: #smtp_address
password: blank or yours
Check to remember the password
Note: user id without user name

And into avast4.ini file at section [MailScanner]:

DefaultSmtpServer=127.0.0.1:25
DefaultPopServer=127.0.0.1:110
SmtpListen=127.0.0.1:25
PopListen=127.0.0.1:110
ImapListen=127.0.0.1:143

Could you check your configuration?