We just noticed something strange:
Shaw's mail server appears to be dropping some bounces.
Our setup is, on Shaw cable ISP, running our own mail server, with Shaw's mail server as our smarthost. Our MX is to our own (Shaw dynamic) IP, so we can recieve mail directly. The reason for this messed up config is that Shaw 1-2 years ago started blocking outgoing SMTP, but they don't block incoming SMTP.
If you have a similar setup (some of you must), try sending email to:
bogususerid@valid.domain.com
and
bogususerid@bogusdomain.com
(fill in the "bogus*" with something you make up)
The 1st (valid domain) one will bounce. The remote mail server (outside of Shaw) will bounce back to you. No problem there.
The 2nd (invalid domain) one will not bounce. It will just disappear.
My current theory is Shaw's mail server is wanting to bounce the 2nd one but looks up the MX and thinks "hey, this is in my ISP IP space" and "no one there is allowed to run a server" and then dropping it.
Any other ideas?
On 06/07/2011 05:48 PM, Trevor Cordes wrote:
We just noticed something strange:
Shaw's mail server appears to be dropping some bounces.
The 2nd (invalid domain) one will not bounce. It will just disappear.
This makes sense to me, shaw doesn't want to send backscatter spam.
I know a few people who avoid the whole dynamic ip/ISP port blocking by using a $5/month vps, openvpn and iptables to provide their home machine with an unfiltered static ip address. Have you considered this?
Peter
Seconded. Different entities deal with backscatter differently so the easiest option for an ISP is to drop undeliverable silently. This wouldn't be the first time I've seen this behaviour.
There are a few BL's out there that go nuts over backscatter (despite it being legitimate in some cases) and a few others use their clout to charge you to get off their lists.
BL's have been losing their morality over the past few years (many are good but the ones being evil are growing faster than the ones being good).
Black lists are evil period. Nothing more than internet vigilantism.
If this is for business why not use a Shaw business account? Those do not block port 25.
Or a better question, why host mail locally at all?
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John Lange -
Peter O'Gorman -
Sean Cody -
Trevor Cordes