Comcast blocking port 25? (not what you think)

[Travis Roy]

>>>Can anybody suggest a workaround.
>>
>>Run the mail server on a different port & redirect.  *sigh*
>>There are some services that will do this.  i'm looking them up right
>>now.
>>
> 
> 
> http://www.dyndns.org/services/mailhop/relay.html is one

That actually seems reverse of what I need, that takes stuff on port 25 
and redirects it to your IP on a non-standard port. I need to have stuff 
  come in on a non-standard port and redirect to port 25.

After some poking around I've found at least two people that can not get 
to my box on port 25 from inside the comcast network, but 4 can.

So it's not isolated just to my parents.