[RndTbl] Shaw blocking port 25 on business line

Sean Cody sean at tinfoilhat.ca
Tue Jan 21 17:03:45 CST 2020

On 2020-01-21 13:36, Hartmut W Sager wrote:
> Shaw seems to have gotten personal and business mixed together in a
> single action.  They are probably cracking down on Shaw personal
> accounts that are "playing SMTP server", which is a common violation
> in the ISP world.
> As for relaying, they ought to accept the use of their mail server for
> relaying as long as you're only doing it from equipment connected to
> your Shaw internet service (and otherwise, they could accept uid/pw
> authenticated access to their mail server).
> easyDNS addresses this problem with their "SMTP port forwarding"
> feature:
> https://easydns.com/features/smtp-port-forwarding/
>  easyDNS, just like Tucows/OpenSRS, is another totally Canadian gem
> based in Toronto.
MX chaining makes for fun troubleshooting but I'm glad it is available 
as an option.

Did you try the submission port (587) and see if that is blocked (won't 
help other than will tell you it was administrative)?  Usually they just 
block tcp/25, cause bots.

One could probably lift the restriction on Shaw by asking the business 
support folk to do so on your delegated subnet or specific MX (also 
consider an external relay for secondary MX to queue traffic when Shaw 
inevitably forgets or something screws up).

Blocking egress SMTP by default is a reasonable ISP policy since 
customers get popped so easily.
Super annoying but they should document and be transparent about it so 
you don't go banging your head against something that should have been 
10 minutes and a phone call.


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