We use McAfee's MxLogic email protection to have them filter our mails before delivered to our Exchange server. The first couple weeks, it did a really good job. But later, junk emails probably figure out how to send emails directly to our Exchange server so now we were told to set up firewall rules to restrict all but MxLogic's IP addresses can communicate SMTP to our Exchange. That really do a good job in terms of blocking junk emails since only filtered mail from McAfee will be delivered to our Exchange server.
BUT it also stops our iPhone/iPad users from sending out SMTP emails using their Exchange mailboxes. They can only receive but cannot send emails after this firewall rule was set.
So is there anyway to work out this issue?