A long-time member of a mailing list posts many off-topic messages, ranging from a couple a month to several a week, and rarely posts on-topic. This behavior frustrates some members of the list because of the noise it generates (both those posts and followups). Direct, private requests to the poster to stop doing this (from several people) have not changed his behavior. Requests to the owners of the mailing list have gone unanswered. Fairly often, now, when he posts one of these messages, somebody will respond to the list asking how this is related to the subject of the list. ("What's the [insert topic here] issue?" is the usual form.)
Aside from issues of what might be effective (that would be a question for a psychology or IT site), how may a (Jewish) member of the mailing list respond? Are the "what's the [topic] issue" responses appropriate, or does the possible embarrassment they cause preclude them? Does it matter if the poster is Jewish? Does it matter if it's a Jewish-topic mailing list -- do we expect a different standard of behavior among Jews than we would on, say, a gardening list? Would it be inappropriate to automatically send all of this person's messages to the trash, which would mean missing any apology or on-topic message he might post in the future?