Please  check the following:

1. The first step in troubleshooting is to make sure that you have a valid E-mail connection on both the sending PC and the receiving print server. Try sending an E-mail message from the PC to a user at the remote site who can receive mail via the POP3 server. If this does not work, there may be an E-mail configuration problem on the PC, on the local E-mail server, or on the remote POP3 server. Double check to make sure that the E-mail parameters that you configured on the PC and on the remote print server match those that are configured on the E-mail servers.

2. If you can print small files OK but are having problems printing large files, the problem may be in the E-mail system! Some E-mail systems have difficulties printing large files. If the file does not reach its destination intact, then the problem is with the E-mail system.

3. You can also enable the partial E-mail print facility on your client PC, this will split the E-mail up into fragments which should then not overwhelm your E-mail server. To do this, select the property dialog of the Brother Internet Print Port, and then check 'Use Partial E-mail Print' box and input 'Partition Value' in the 'Safety E-mail Sending Options' section.