Subscribe to Autoresponder from sent e-mail message (rather than block)

Issue Summary

Does the module have support for subscribing users to an Autoresponder list if they send an e-mail to a pre-specified site e-mail address?

Here's a bit more explanation: We need the ability to sign up users without necessarily using the Autoresponder block. Many visitors on our websites send us e-mail messages and we would love to set it up so that messages sent to certain e-mail accounts automatically sign up the user for a series of Autoresponder messages. Is this possible in the 5.x-1.x-dev version of the module?