Q.: "mypixmessages.com"? (MMS via PagePlus on VZW network)

[tlvp]

So I snap a photo with a PagePlus-activated Verizon-branded handset and
send it for safekeeping to an email address I maintain. It arrives there in
good shape, seemingly from [My10Digits]@mypixmessages.com. Great!

But: there's no DNS entry for that domain, mypixmessages.com. And perusal
of the headers of that MMS, as received at my email account, reveal as
hand-off domains involved in the transmission of that MMS message, only
vtext.com, vzwpix.com, and myvzw.com:

> Received: from njbrspamp3.vtext.com ([69.78.129.148])
> by [MyMSP].net with ESMTP, Sun, 4 Nov 2012 15:45:17 +0000
> Received: from 88.sub-66-174-71.myvzw.com (HELO m18.vzwpix.com) ([66.174.71.88])
> by njbrspamp3.vtext.com with SMTP; 04 Nov 2012 15:45:17 +0000
> From: [My10Digits]@mypixmessages.com

So: what's really going on here? What's this mythical/virtual sender domain
mypixmessages.com doing? (BTW, [MyMSP] is my own munging of my Mail Service
Provider's actual server name, and [My10Digits] is my own munging of the
ten actual digits (area+exchange+FinalFour) of my cellular phone number.)

TIA. And cheers, -- tlvp


--
Avant de repondre, jeter la poubelle, SVP.