ISP port blocking practice

Thu Oct 22 23:14:11 UTC 2009

> Few 
> companies use the MSP port (tcp/587).

Can you elaborate. Is this based on analysis you've conducted on
your own network? And if so, is the data (anonymized) available for
the rest of us to look at?

My experience is that port 587 isn't used because ISPs block it
out-of-hand.  Or in the case of Rogers in (at least) Vancouver, hijack
it with a proxy that filters out the AUTH parts of the EHLO response,
making the whole point of using the submission service ...  pointless.

--lyndon