KT,
Firstly, make sure that you can send and receive email properly regarless of whether it is presently being scanned.
Secondly, send an email to yourself to ascertain if the "outgoing mail" is being scanned.
Thirdly, once this is done, go into your options in your email client and make sure the configuration is correct.
Fourth, open up the Avast On Access Protection Console and then Standard Shield. Make sure that for POP, SMTP and IMAP, the "Insert......" box is checked.