This is copy/paste of one of my latest posts on this topic:
Try to set all those inbound and outbound data and account name and passowrd as it was before you installed avast! (your mail provider information). Click APPLY and OK, and close Outlook Express...
Go into your avast! directory and manually start ashPOPwz.exe file.
Click NEXT and under BASIC SETTINGS choose AUTOMATICALLY PROTECT ALL MY ACCOUNTS and put checkmark under AUTOMATICALLY PROTECT ALL MY ACCOUNTS THAT I CREATE IN THE FUTURE. Click NEXT again. Under smtp server settings, type your smtp server name (in your case your mail provider's smtp data)... under default POP3 server input your default pop server name (it doesn't have to be your default mail provider if your primary e-mail address is somewhere else). If your primary e-mail account is at let's say Symaptico, then input your Sympatico pop3 server name...
Click NEXT, then FINISH and that's it...
When you open your Outlook Express again, go to tools/ACCOUNTS and choose to see properties of your default e-mail account. Click on SERVER tab and you should see 127.0.0.1 under both, incoming and outgoing mail settings. Those settings are correct.
Type your password again into password box just to be sure...
Take a look below... under Outoging mail server section... If your server requires authentication, check that checkmark and set those settings as they should be set...
I hope this helps... we all have set those settings like that and everything works just great... avast! rulez !!!
In case it doesn't help you, please post again and tell us if you use some of those spam killers, and exactly which one...
Cheers !
Hope this helps !