su - zimbra
zmmsgtrace -r 408XXXXXXX@messaging.sprintpcs.com
Does it leave the system? It's possible that sprint is dropping it because your mailserver's reverse DNS doesn't match it's hostname.
I get this error when i run the trace. Does that mean sprint does not like my server? Thanks again
(connect to mx.messaging.sprintpcs.com[18.104.22.168]: server dropped connection without sending the initial SMTP greeting)
Probably, if they didn't even send an SMTP greeting.
Since you got dropped before the EHLO exchange, it probably means that you're listed in a dns black-list somewhere, or they just block port 25 connections from your ISP as a matter of course. (Are you on a cable modem, or a large provider's DSL network?)
You might try relaying through your ISPs gateway.