<OT> what is a port?

[Tony Alfrey]

Please excuse the total newbie question.
Our tenant has a mail account on her cheap domain hosting service (OLM), 
which uses *only* port 25 on their smtp server.
We are on Comcast cable which blocks port 25, so you see the potential 
conflict.

But I don't get it:  what is it about the "packets" that are shuffling 
off presumably first to some Comcast server and then to the server on 
OLM that "tells" Comcast that there is something unacceptable about the 
"port"?  Why should Comcast care about the "port" since it is the OLM 
smtp server my tenant wishes to "speak to", not the Comcast smtp server? 
  Or perhaps a related question is:  why is the internet accessible 
without reference to a "port", presumably on the Comcast web server?
Thanks!


-- 
Tony Alfrey
tonyalfrey at earthlink.net
"I'd Rather Be Sailing"