[tde-users] email mess - maybe OT or not

There is a recurring glitch in my emails, which involves another person (person A) here on the mailing list. (I don't name him here, but I have already contacted him to ask about it.) It involves the mailing list, maybe, because I only know him from the list, and we have only exchanged a couple of personal emails outside the list. Now here is the actual "problem": I have another friend (person B) who is not a member of the list. When she recently sent me an email from her phone, the private email address of this first person (person A, a member of the list) showed up in her (person B's) email headers. There is absolutely no other connection between these two persons, except of course for myself. I went through other email correspondents, to see if something similar was happening, but it only seems to be with these two people. I created an entirely new email (no metadata from replies, etc.) to send her (person B) something, and again I found person A's headers in this email that I sent. So it doesn't seem to matter if person B or myself initiate the email; the headers from person A (who is a member of this list) always show up in the headers. Sorry for the vague description, but I am taking pains to avoid mentioning names. If person A (member of the list) chooses to join the conversation, then I can speak a little more freely. And let me make it clear that I do not suspect either of these people of anything at all, as they both seem as clueless as myself about these matters. Can anybody offer an explanation for this email quirk? I bring my question here, because it involves somebody else who is a member of the list, so that it might be a concern for other members of the list, and of course for the moderators, Slavek, et al. I would be glad to offer a sample of the headers, but I also need to consider the other persons involved. Bill