Thought so.
You can have that scanned now along with avast using the third party STunnel software. Let us know if you wish to do so and need any help ... the search function in this forum can guide you too.
If you can wait a little longer then, probably by the end of the year, the equivalent function of STunnel to help you work with secure ports to get email scanned will, most likely, be provided within the next release of avast itself.
If you gotta have it now then you can also use the Webmail extensions of Thunderbird (as I do) to get your Yahoo mail scanned but that is similar to YPops and breaks when the Yahoo folks make changes. You can get help here with that too or wait for avast 5.0 ... up to you.
I recommend staying as you are until avast 5.0.