How to detect forged From and Reply-to addresses from your own domain

[Glenn Steen]

On 8 March 2010 18:17, Michael Masse <mrm at medicine.wisc.edu> wrote:
>
>
>>>> Mark Sapiro mark at msapiro.net> 3/6/2010 11:19 AM >>
>
> My ISP redirects all port 25 connects to its own servers so even if I
> know what I'm doing, I can't use your MTA for my outgoing mail for this
> account.
>
> I've heard of ISP's doing this with port 25, but not 587 which is a standard
> alternative port for smtp submittal.  Are there ISP's redirecting 587 as
> well?

None that I know of... And doing so would entirely defeat the prupose
of "blocking" port 25... Doing that (as an ISP) is a service to us
all, so that mass-mailer crap just can't function. IIRC the swedish
ISPs were among the first to do this on a large scale... Made telia.se
move from one of the worst "spam sources" to one of the least
affected;-).
Since the alternative port come with an authentication setup, it fits
the purpose perfectly... And hence the ISPs just plain don't have any
valid reason to block it.

> -Mike
>

Cheers
-- 
-- Glenn
email: glenn < dot > steen < at > gmail < dot > com
work: glenn < dot > steen < at > ap1 < dot > se