Are the SPF port only used to inter-connect switches?

Is this a good choose for VoIP in a small office (under 300 user's)??

Hi,I'm having an issue with a particular spam email. It never comes from the same domain, but always include a .gif file with a stock quote attached. I looked at the internet header to try and find something unique to base a custom signature. Here...

I'm getting hundreds of triggers on signature 5748 Non-SMTP Session Start. When I put a block host on this signature I stop getting e-mail. Should this be considered normal traffic.