I am the beneficiary (or victim, depending on how you view it) of Cox Communications turning all email services over to Yahoo. Both Cox & Yahoo store messages on an IMAP server. As seems to be Yahoo's custom, they provided minimal documentation. Last night, in a 3+ hr call to tech support, for example, I noticed that my inbox had exactly 10,000 messages. (I know. It's not Inbox Zero -- I'm a bad, bad boy.) This seems suspicious, so I asked Yahoo's tech support agent about it. At first they said Yahoo puts no limits on messages and blamed Thunderbird for this. Then I showed them my employer's Gmail inbox with 35K messages and said this proves it's not Thunderbird. Then the agent said Yahoo has no limit. Then, apparently after getting feedback from their "support team," they said there's a limit of 10,000 messages per folder. So, even Yahoo's tech "support" seems almost clueless about such undocumented "features." I know I need to trim the inbox, but I also need to keep lots of messages currently in it. So, the first thing I have to do is to move a large number of messages from the Inbox to another folder whose contents will be fixed. To do this, I first created a folder to keep the original messages, "Cox Inbox." Then I created a message filter with the following logic: * Match ''all'' of the following: Date, is before, 4/7/24 (the day before Cox migrated my account) * Move message to, Cox Inbox But despite trying this repeatedly (I also tried "Match ''any'' of the following"), most messages stay in the Inbox and relatively few make it to the "Cox Inbox." I don't know how to troubleshoot this. Can you help? Not being able to get the filter to work, I tried brute force. In my Inbox, I highlighted all the messages I wanted to move, pressed CMD-C (I'm using a Mac), went to the Cox Inbox, and pressed CMD-V. But it seemed nothing happened. Again, I'm at a loss as to how to troubleshoot this. Please help.