Can it be used with Hotmail, Gmail, Yahoo?

Business / Enterprise Security Products & Services Comodo AntiSpam Gateway - Hosted Anti Spam Service
1

I now this is a dumb question…
Is it possible somehow to use CASG with hotmail, yahoo, gmail, etc?

Someone had to ask. 88)

2

For now it is possible only with owned domains.
The restriction is in ability to change MX record for the domain.

So no - for gmail.com
But if you have write access to DNS MX record for yoursubdomain.gmail.com - then yes.