Email to SMS problem

I have 2 email messages in my email client. I can send both of them to xxxxxxxxxx@att.txt.net in both cases, the mail goes through... no bounceback, AT&T email servers take the message. In one case, I get it as an SMS in a few seconds, in the other case, never. This is completely repeatable, AND, I have tested it with other AT&T phones. Always the same. Both of the messages are comprised of simply a URL. One is a shortened URL (goo.gl, but tinyurl behaves the same) the other is long. The shortened one does not get delivered.