On 18/12/2019 11:51, The Natural Philosopher wrote:
On 18/12/2019 11:41, Chris Bartram wrote:
On 18/12/2019 10:04, The Natural Philosopher wrote:
On 18/12/2019 09:31, Sn!pe wrote:
Back in the day, ISPs would commonly hijack port 25 SMTP traffic
and silently push it through their own SMTP server instead as an
anti-spam measure.Â* Even though nowadays other ports are used,
is that not still the case?

I think only BT has the power to do that. And possibly mobile operators.


BT at one time used to block TCP/25 to anywhere but their own SMTP
servers for domestic customers. Not sure if that's still the case.

Are you sure?

https://community.bt.com/t5/Archive-...25/td-p/413447



Pretty sure, yes. One place I help support had it's own branded ISP at
one time, back when you had to pay for dial-up time. We discontinued
that, but had to retain the mail domain and migrate it elsewhere. The
users migrated away for connectivity to other ISPs, but retained the email.

Then one day, the SMTP stopped working for BT customers, so loads of
support calls.


That is a horrendous situation if true.

It certainly isnt true now as a friend uses my relay to send no problem
via BT


Indeed. I think they thought better of it.