forward and append gmail subject with sender's email address

I need to forward mail messages that append the subject with the first part of the sender's email address. So for example, our VoIP service sends a gmail when a user gets a voicemail but the subject only reads "voicemail message." The sender is the phone number at the VoIP domain. So the sender would be 555-555-1234@voipdomain.com. I want to take the 555-555-1234 and forward and append the subject so the subject reads "555-555-1234 Voice Message." And ideas?