I installed Symantec Endpoint Security in an unmanaged network back in January 2008 with very few issues.  A few weeks ago I upgraded the firewall from a Watchguard SOHO 6tc to an Edge X55e.  After the switch we began experiencing SMTP time out errors in both Outlook 2003/2007 & outlook express.  Disabling the Network threat protection fixed the issue temporarily.  The only permanent solution was to put back the old SOHO 6tc.     The settings are identical on both firewalls.  Both Watchguard and Symantec tech support were contacted but have not been able to fix the problem.  Has anyone else had the same experience and if so do you have a solution?

Regards