As far as I'm aware there are no intentions to implement an antispam tool. There are many freeware and paid for options out there.
I use MailWasher Pro, although it is primarily for Spam it is also easy to deal with suspicious emails too. There is a free version, but this only works with a single email account. The Pro version works with multiple accounts.
I use it independently of avast, an IgnoreProcess=MailWasher.exe in the MailScanner section of avast4.ini. I believe having the limited part of an email which is view as a text file (without attachments) is a very limited risk and an unnecessary overhead.
There are a number of suitable antispam programs you can integrate to work with avast.