I'd recommend PM'ing him and explaining that using an e-mail address as a username causes a few problems. Not only does it open him up for becoming the serious target of spammers, but it causes problems within the forums because the software doesn't know whether to treat a link to a username as just that or as an e-mail link. Therefore he can request a different username or, if we don't hear from him, we will change it to just cgha20 (assuming that's available).
@jrap: If this practice is not against the ToS it should be, if only because of the logistical issue of interpreting links. For instance, I can't follow the link in Dick's post to get to the guys profile because it wants to create a new e-mail to him. That had me scratching my head because I couldn't figure out why Dick was posting some user's e-mail address or having an issue about him making 65 posts -- until it finally dawned on me that it wasn't supposed to be an e-mail link, but rather a link to that guy's profile and that the e-mail address WAS his username. At which point the answer to my confused question of, "What is 'this user name'?" became obvious.
He is an old member. (21 oct 2009).
Nowerdays it is not possible to use an email address as username.
We could offer him to cut off the email domain from the username.
The name cgha20 is still free.