iPhone Email Ports / Problem Sending Mail

After the 1.01 update, I noticed at least a 60 second delay in sending mail from iPhone that is configured to exchange server. The only ports I opened in my firebox were 143 for IMAP. When I am inside the network and not going through firebox, the sending of email is instantaneous. Are there additional ports I need to open??? Or what else can I do to allow instantaneous sending of email while outside the network and going through firebox??

Thanks
LBW