<OT> what is a port?

vu pham vu at sivell.com
Fri Oct 17 10:38:20 PDT 2008

Tony Alfrey wrote:
> 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?

I think that they want to limit the spam mails. I had similar problem 
before with my previous ISP SBC. I could not access my company mail 
server without using VPN when I was at home. Of course, I can use VPN to 
access it, but sometimes I need to check problems for customers, so I 
need to be able to check connections with my naked system, not VPN. I 
remembered I chatted with SBC tech support around 10PM and told them 
that why I need edto access port 25 on remote systems, they found it a 
reasonable request so they unblocked it.

Personally I think it is the mail server owners are the people who are 
responsible for blocking spam mails, not the ISP. The ISP may own mail 
servers, but they should just limit the spam mails by setting up 
filters, rules on their mail servers, not on the network.


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