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I don't believe groups.io has anything misconfigured on their end, so I'm not sending this as a "bug" or support issue.? Mostly I'm putting it here to help other moderators/owners in case you've dealt with this, and to give some advice for remedy.

I have one group member who was unable to receive any groups.io emails.? Groups.io was showing the following error for all email deliveries to that one user:??us-smtp-inbound-1.mimecast.com: 554 Host network not allowed -?

In this case, their company uses a service called Mimecast as their company inbound anti-spam/anti-virus email gateway. From the error I was able to determine this is a result of them having implemented the geographic blocking functions of Mimecast to block emails from outside the US. Here's the interesting thing:? I also use Mimecast for my company email gateway, but I do not implement geographic blocking.??I tracked groups.io emails coming into my organization, and they all came from a single IP that, when I perform my own geo lookup, is identified as coming from California.?However when their IT group researched the blocked emails, they?determined that Mimecast was identifying the source IP for the groups.io emails as originating from Hong Kong.??

In this case, the "fix" is entirely on the receiving organization (they did implement a permit rule so the groups.io mail server IP was whitelisted), but you should be aware that this kind of blocking can occur from time to time, and is not explicitly something that groups.io can do anything about... but as a moderator/owner, you have the ability from the email delivery history for a user to get this kind of information to help your members diagnose why some emails may not be delivered.

For reference, the IP identified as the source for groups.io emails in my tracking is?66.175.222.12

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Bryan Jones
Kenwood-Hybrids group co-owner/moderator
TECSYS EliteSeries user group owner/moderator

On Fri, Jan 17, 2020 at 09:40 AM, Bryan Jones wrote:

I tracked groups.io emails coming into my organization, and they all came from a single IP that, when I perform my own geo lookup, is identified as coming from California.?However when their IT group researched the blocked emails, they?determined that Mimecast was identifying the source IP for the groups.io emails as originating from Hong Kong.??

Yes, io is a top-level domain for the "British Indian Ocean Territory," which may at one time have included Hong Kong. If a receiving provider uses very crude geographic filtering (tld instead of IP address), it could be a problem, and the subscriber needs to find a provider that doesn't.

Personally, I consider groups.io to be a global community...no one is a "foreigner." In that context the filtering of messages on such a basis seems rather absurd.

Regards,
Bruce

Bruce,

Mimecast is not a "crude" provider of anti-spam/virus filtering. It's one of the industry best.

Regardless of your perspective of the mission of groups.io, you have to respect the needs of every organization to implement protections against malicious email.? Fully 4 out of 5 of all emails on the internet are garbage - any organization NOT implementing protections against that is what I'd characterize as "absurd".

My message was posted as a bit of a "PSA" to help moderators who may be seeing bounced emails due to anti-spam filtering such as this (particularly when they're interacting with people who are using their professional/business email when the group membership is relevant to their professional responsibilities), so as to help them understand that in many cases it will require a collaborative effect, involving the recipient's IT support, to resolve undeliverables.? It's easy to blame groups.io when something doesn't deliver... as someone who has performed systems administration for email systems for decades, I can say that it's FAR more often that email delivery problems are the result of issues on the recipient's side, than it is a result of issues on the sender's side.

I really enjoy the fact that the groups.io platform exposes the errors encountered when bounces occur... it gives me the information needed to take it to the next step.

Regards,
Bryan

I did a deep dive on the origins of the .io TLD.
Very interesting what happened.
Even though the British had a big role in things way back,
it is basically not used by "only" one country...
(Or JUST those Islands.)
The filtering method used is bogus...

Rick

You might be interested to know that Mimecast tech support has confirmed that the IP geo database they are using is, in fact, identifying the IP itself for groups.io's email server (NOT the TLD) as originating in Hong Kong.? So some IP geo databases identify it as originating in US, and some identify it as Hong Kong. The filtering method itself is not "bogus", nor "absurd".? It is simply using a flawed database. This could easily affect any type of spam filtering engine, including those used by public email providers, not just corporate email systems, if they are using that database (or any other IP geo data feed that also uses that data source (i've identified at least 2 more).

Just trying to give other moderators a "heads up" that this can cause email blocking for their groups.

--?
Bryan