yea, I can send and email to the account from my gmail account fine. Logged in with the user cendent, and read the mail from the gmail account.
I can also send mail to my gmail account with user cendent, I think this is because gmail doesn't require a user auth.

Well I don't, since you can send to gmail. From what I can understand, the other server (syndicate-gaming.com gets) gets confused about the user (same uid) at your server (criminal-syndicate.com), when it tries to verify if that user actually exists.

Yea your 100% right about that :)

I have my domains registered through a different hosting company with the dns pointing to the correct servers. But when I'm sending between two of the domains it looks for a local user and never bothers to do an actual dns lookup makes sense, all is working.

Thanks a bunch for all your help.