I’ve tried several times to join this site and everytime I try I get rejected and told I have to provide a valid email address. For some reason, it won’t accept my perfectly valid email address. This has occasionally happened to me with other sites. Any ideas as to why this is happening?
anything we should know about your email address?
No, it is nothing special, just a regular Comcast address.
This is just a wild guess. Did you remember that Comcast addresses end in .net rather than .com ?
Yes, I did.
What’s the time delay between applying and being rejected? Seconds, minutes, hours, days?
I have a sort of simple email addy, and I often get things where obviously someone signed up for something using my addy as a dummy. But you’d have gotten a message to that effect had that been the case, I would think.
Seconds. I put all the information in the “Join Up” form, press “Join” and get the message that I must include a valid email address.
Do you have the ability to create “child” email accounts via Comcast? If so, have you tried setting one up and registering it?
Have you tried setting up a Gmail or other “disposable” account and registering that way?
I can’t think of a valid reason your regular account wouldn’t work unless it has been flagged in some way by them. As a last resort, I’d try emailing their webmaster and pitching a fit. 
My guess would be that they’re using a crappy regular expression to verify the email address. Do you have any special characters in there, like an _ or a . ?
No
My wife figured it out. My Comcast email address has a period in the middle of it; she said some sites, especially older ones, will not accept such an address. So I’ve joined using a different address. Thank you all for your suggestions.
Good work, ptr2void.
I want to apologize to ptr2void. When I read his post I completely missed that he had mentioned a period as one of the possibly complicating factors. When I asked my wife for her ideas, she independently came up with the same idea. But I wouldn’t have had to ask her if I had read his post more closely. On the other hand, as she pointed out, if I had asked her first, I wouldn’t have had to make my original post!