Harvey (and any other readers),
in the redirect ports tab, if port 25 is specified and the Internet Mail Provider is active then the outbound mail traffic is still intercepted by Avast. Whether that traffic is then scanned is determined by the "scan outbound mail" checkbox in the SMTP case.
This is true for all the intercept ports in Internet Mail Provider. Should one wish to have the provider active and "opt out" of having a particular class of traffic intercepted (for example NNTP) then it is necessary to ensure the the real port used is not specified to Avast.
At present, I believe that you have identified a real performance flaw in the SMTP scanning of Avast. I shall be interested to hear the response from the Avast team.
In the great scheme of things though, having my email take a bit longer to be scanned outbound I can live with. Especially at the price point I pay for Avast which is, I believe, a great product.
I am not a bigot on these products. If you check the e-mail forum of AVG you will find a "sticky" under my userid. I did test it a while back and I got my e-mail to be scanned.
I honestly believe that the email scanning is easier in Avast. On one thing I regret I cannot defer, the support in this forum and the direct participation and assistance of the Avast development team cannot be matched by AVG.