ISP port blocking practice

Owen DeLong owen at
Fri Oct 23 03:51:09 UTC 2009

On Oct 22, 2009, at 4:14 PM, Lyndon Nerenberg (VE6BBM/VE7TFX) wrote:

>> 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
Wow... That's evil.  Most ISPs I've dealt with don't have that  
problem, but,
if I encountered one that did, I'd vote with my feet in short order.


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