Very nice, and I think I see the problem here...
I;m a big fan of your site and the mailbags. Before I review this, I'd like to note something about the people saying that this is like the Strong Bad Emails. I personally don't think that your Mailbags are that similar to the SBEmails, but this PARTICULAR one seemed more like an SBEmail than most. Usually, mailbags consist of multiple characters, behind-the-scenes references to the site, and discussions of current games and technology, all of which set it apart from H*R. This one, however, followed the standard SBEmail formula of one email-one funny resulting skit-end with easter eggs. So, I can see why people said you were ripping off H*R, even though I know you weren't trying to.
As for this actual Mailbag, It was good. Sceb's delivery was funny and the ad had some funny moments. My only real complaint here is that the easter egg at the end was rather unsatisfying. I'm not sure if something's supposed to happen with Clydex because I stopped watching him look around after like two minutes, but something more could have been done there.
Personally, I think that you should submit some of your other mailbags. Not only are some of them much funnier IMO (not that this isn't,) but most of them are much less Homestar-esque than this particular one you submitted.
But hey, they're you're cartoons and you can do what you want. Hope you keep making them, because they're really great.