sonic tz180 hotmails not deliverable

I opened up my firewall to allow access to more url’s and found that when i try to send to hotmail addresses they get returned undeliverable with this message:
The following recipient(s) could not be reached:
‘t******@hotmail.com’ on 4/11/2009 1:15 PM
Could not deliver the message in the time limit specified. Please retry or contact your administrator.
<**************.com #4.4.7>

Im Guessing it has something to do with SMTP but it is only doing this with hotmail accounts
Thanks up front