On Thu, Jan 3, 2019 at 01:52 PM, I wrote:
Definitely a puzzle.
...which seems to be been resolved, at least for now. Our afflicted member has had another session with his ISP (videotron) and reported back to us as follows. The only edit I have carried out is to anonymise our Group
During the last month (December 2018) there have been 57 reports from one or several users of videotron.ca e-mail account(s) that the site <Groupname>@ groups.io is a SPAM one ! The e-mail server automated SPAM list triggers on, past a certain level (I guess that is 50 rports or more) and a new ¡°filter¡± is applied on the 1st day of the next month.
The automated action of the Videotron delivery system is then to simply DISCARD all the e-mails coming from the site, whoever the e-mail recipient !!! INCREDIBLE¡ but that explains why I stopped to receive messages from the site at noon, local time, on Jan 1!
Our member added The videotron engineer who talked to me is sure that the automated reaction was triggered by one or many users trying to unsubscribe by just using the SPAM button on their Videotron web-based e-mail interface!
A test email from the web UI cartainly worked when the system was tested again, but I am not entirely convinced by the explanation. We have a grand total of four members with videotron.ca email addresses, and two of them are set to Special Notices only, so if the reported explanation is correct it would suggest that this blockage was caused by a single member persistently reporting Groups.io messages from our group as spam.
What is a bit worrying is that an ISP would accept these "reports" as correct and simply stop passing the traffic to recipients while at the same time accepting them from their originator without comment, as evidenced by the 2.0.0. delivery reports.
We will have to keep an eye on this to see if it happens again. I might email the other "individual email" recipient to see if he noticed (or did!) anything untoward.
Chris
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