Mail lists no longer sending e-mail messages - except if thread created by poster

I am suscribed to five Trisquel's mail lists, and I used to receive the e-mails. However, yesterday I went through my e-mail folders and verified that not a single trisquel mail message had been received since the last time I emptied my Trash folder, on April 25.

My first guess was that Mailman had mistakenly unsuscribed me, therefore I sent an e-mail test message to trisquel-users with the subject "Test: Subscription to Trisquel-users no longer working through mail list".

However, the message was accepted immediately, and its thread is viewable at Trisquel's website: Test: Subscription to Trisquel-users no longer working through mail list | Trisquel GNU/Linux - ¡Vai por libre! https://trisquel.info/gl/forum/test-subscription-trisquel-users-no-longer-working-through-mail-list

In fact, other users reported experiencing the same problem, one of them mentioning April 1 as the first date. I received my own message and its replies - but still not a single message from the other threads. It seems that I am still suscribed and can send messages, but get only my own messages and their replies. A faulty and odd behavior from Mailman.