[LINK] RFI: Email Download Failure from Local ISP

[Scott Howard]

On 1/22/08, Jan Whitaker <jwhit at melbpc.org.au> wrote:
>
> I know nothing much about this stuff, but I've been seeing that some
> ISPs in the US are shutting out 25 and going to 2525 as an
> alternative. Could that be it?



Not unless they don't actually want people to be able to send mail to
them...

In order to receive mail from the internet you _must_ use port 25. Simple as
that. No way to change it.

What you're probably referring to is the port they are using to allow their
own customers to connect to their mail servers to send mail.  This can be
changed (although it requires your customers to change their config to
match), and there are often good reasons for doing it.  The more normal
ports used for this are 587 or 993 (for SSL), although there's no reason an
ISP couldn't use 2525 - it's just non-standard (587 and 993 are RFC'd
somewhere).

  Scott