Port 25 and Static/Dynamic IP for Listserve SW

[Smoot Carl-Mitchell]

On Sat, 2009-07-18 at 11:35 -0700, Piper wrote:
> Port 25 is just the normal SMTP port isn't it?
> 
> So if I bcc this to 50 addresses of the ABC list in my Express mailbox it 
> goes through Port 25 to all 50. And it uses a "dynamic ip" address.
> No problem.

Only because your ISP recognizes you as a customer.  Try to send the
same mail to another ISP.  These days most ISPs also require you to
authenticate to the MTA.

MTAs also listen on port 587 which is the mail submission port.  I have
known ISPs to block all outbound connections to port 25 and only allow
connections to port 587 of the their own MTA.  This was particularly
aggravating, since when I am roaming, I forward mail via an
authenticated connection via my own MTA on port 25.  I had to change the
whole setup to use port 587.

-- 
Smoot Carl-Mitchell
Computer Systems and
Network Consultant
smoot at tic.com
+1 480 922 7313
cell: +1 602 421 9005