virus@avast.com will do nicely.(The file is best zipped and password-pretected. Include the password in the message body.)
I think what Safesurf is suggesting is that you might want to check them first by uploading them (one at a time) to the virustotal site, which is a multi-scanner file checker. (42 different updated AV's check uploaded files, I think).
They can also be submitted from the chest. See
here You should not always expect a reply by email, the guys and girls are maybe too busy for that; I'd imagine they get hundreds of submissions.
Any reply would take the form of the file concerned being detected by Avast in the future. (Or a false positive being
not detected.)
The forum has no facility for virus analysis, and is not a place where virus samples are traded, as far as I know. If it is, it would be a private matter between forum members, and not public.