No, it's a replaced alias for my real gmail, and it has nothing to do with a birth date or subscription date.
But I've not posted using this address I don't know (that's the first time I see it). It's may be an alias created by this mailing list (to protect the privacy of subscribers), or possibly by Google (or created by this list on Gmail with a redirect specific for this list, possibly following the instructions Gmail gave to list maintainers, or because this Gmail address accepts messages redirected from other mail accounts I own), but I was not aware of this fact. I don't know if this alias is valid and will finally reach me, I've not tested it.
Even my true name (before the mail address) has been aliased to a single letter.
