If you have recently updated your AVG to version 7 and you are using Thunderbird as your email client on Win XP SP2 it probably will not work with Zone Alarm. To make it work ,first disable the email scanner in AVG by selecting it in AVG control centre and then choosing properties/disable plugin.
Go to Zone Alarm,choose Program Control / Programs, scroll the list and find AVG e-mail scanner and AVG Update downloader, and make sure all the question marks in the Access,Server and Send mail boxes are changed to Green ticks by clicking on them and choosing "allow". Now go to Firewall/zones and click on add>>
choose IP Address and type in the IP address of your mail server Ex, give this a name in description ie "mail server" and make sure Trusted is displayed in the Zone drop down list box. Choose Ok.
Go back to AVG control centre and re-enable E-mail scanner plugin. All should now work OK. I hope this helps,Cheers GWS.