The first email didn't go through multiple mailing lists because each one have different acceptance criteria (different size limit, membership criteria, etc.) and some accepted it, some held it for moderation, some rejected it, some discarded it (without rejection notice). There is nothing unexpected about it.

The second email went through some but received only once by people and that's also intentional, most major mail providers de-duplicate emails coming to the user. e.g. if I'm a member of mailing lists A and B, and someone sends an email with cc both, mailman sends it to me twice but GMail discards second one. That's why it's also recommended to cc in one email instead of sending it multiple times.

I'm inclined to just mark this ticket invalid.

I posted the message in two batches:

1. to all mailing lists, CC-ed
   • it was rejected (not held) by some lists, as Ladsgroupe explained
   • you received it seeing the cc-ed lists, but as the message was rejected, it never came there.
2. I subscribed to the mailing lists that rejected my message and posted again to the missing ones

And yes, a unified policy regarding moderation would be nice to avoid these issues.

I still have the issue when I post MediaWiki train related messages to both ops-l and wikitech-l. I then end up wondering whether the email reached both list and have to head to the list archive on https://lists.wikimedia.org/postorius/lists/ to confirm.

Sending a single mail to multiple lists at once has always been discouraged though, to be honest.

The thread https://lists.wikimedia.org/hyperkitty/list/wikitech-l@lists.wikimedia.org/thread/RCKRQ2GKRVLGVLFJMOCURY3BYM4GOWYA/ had two replies sent to both mailing lists and directly to me. Despite having the Receive list copies setting enabled in mailman, I only received the emails that were sent directly to me (the mail headers do not show any traces of Mailman in the routing.

I have checked my list-based preferences for both wikitech-l and ops and I did set the preference to receive duplicates:

Receive list copies (possible duplicates) | Yes No

When you are listed explicitly in the To: or Cc: headers of a list message, you can opt to not receive another copy from the mailing list. Select Yes to receive copies. Select No to avoid receiving copies from the mailing list

My Address-based preference at https://lists.wikimedia.org/postorius/accounts/per-address-preferences/ does not have any option ticked and my Global preferences at https://lists.wikimedia.org/postorius/accounts/mailmansettings/ do have the Receive list copies option ticked.

This all leads me to believe Mailman does not honor that option and does not send me the emails. The messages id of messages that were not sent to me by Mailman are:

Message-ID: <CAELUtevU6PwpycEyYAG4wBrW3-gk+OziSqHQwq+UXBNkN5QM+Q@mail.gmail.com>
Message-ID: <CAEVcXn2etbCAhL3a5Nnbv6D48R4otKDiBBtD+uWEavC+nyou-g@mail.gmail.com>

I don't have access to the Mailman / mailing list logs to check whether those got sent to my email. If my assumption is true, those Message-ids have never been sent to my email which would be a bug in Mailman.

But "Receive list copies" is just about receiving copies of your own posts. So I'm confused why it's now about replies to your posts and gmail.com messages. Your own posts are from a different provider.