I use Thunderbird on multiple servers as an IMAP client. I update TB automatically. I sometimes get multiple copies of emails. They usually are in boxes into which I move emails automatically with rules, but occasionally in my inbox as well. I have not yet seen any duplicates in my sent mail on any server. Can you tell me likely causes? One of the problems we are having is occasional loss of internet signal (I guess we're at the end of the web :)) so could this be a manifestation of that problem? If I run a duplicate check, the program will identify all as duplicates. If it were connection only, I'd expect to sometimes get 3 or more copies as well, but I only get two. Is there a fix for this annoyance? It happens mostly on yahoo! (the only email on which I run filters, but also the one that I notice sometimes that it takes forever to save an outgoing or draft message) but occasionally I have seen it on gmail server and Microsoft 365 server as well. Webmail shows no duplicates on any server. I have cleared the index files, etc but that does not seem to be the solution. This is intermittent, which is why I am thinking it may be an intermittent internet problem. I'd like for it to not happen, so is this a possible problem to fix in Thunderbird? Thanks, Russ