The "moderator" of this board uses gMail for a few reasons:
1.) "Unlimited" email storage. While the sender of board emails uses this server's SMTP; having gMail for the registration allows us to save millions (if not billions) of emails from users whom we've activated.
2.) Registration emails (and assumingly notification emails) don't seem to be received by everyone. Many overseas hosts block US IP addresses (for what reason, I'm not sure). gMail; however, doesn't seem to be blocked. So gMail offers us an easy way to know we're getting emails out to you (unless your inbox is full, as some people's accounts are
)
3.) Thomas uses a gMail account because before this forum was here, all requests and bugs were put in to him. So he had a nice large mailbox to receive his roundcube emails. Not to mention that it saves him from actually divulging his true email address.
Hope that explains some things to you. gMail is not the devil, and it works almost everywhere while personal SMTP servers (because certain people can't secure their own servers) are blocked.