Why not just send an e-mail from the account to myself or another reputable member? The picture above doesn't prove ownership at all, you could have quite easily: a). doctored the phone b). asked the owner to send you some proof that they own it by sending that message.
It looks like you've got no issues sending e-mails from the domain, in which case just send an e-mail to my email (iliketosellyoustuff@gmail.com) with a link to this thread and I'll happily purchase.