Hello...thanks in advance for assistance on this issue.

I am running postfix 2.3 and I am trying to enable a few users to send outgoing mail through our smtp via port 587. I altered the master.cf file to enable the entry:
submission inet n - - - - smtpd
-o content_filter=spamassassin

I also allowed packets through the firewall from this port and was able to send mail via this port from outside the network, however, I cannot seem to utilize this port to send mail from within the network.

For example, I have an iPod Touch that is set with our smtp server as the outgoing mail server and it is set to use port 587 (being that port 25 is blocked by my home ISP). At home, it works fine, I can send mail all I want. Once I am back at work, within the network, I cannot send mail via this port.

I checked the firewall, this port is not being blocked. I also don't see any entries in the firewall log to this regard. I'm guessing its a postfix issue, perhaps I am missing something above. I've checked the logs for my device, I can see that it is connecting to the smtp server, but disconnects. I don't see much else.

Again, any help is greatly appreciated.