[Bender]

Just a suggestion, enable IMAP in yahoo and generate an app password. Use something like Thunderbird to "move" all your emails off their server and onto Thunderbird locally. Get in the habit of exporting and backing up those emails. Then your mailbox will not be full and perhaps the messages will stop. Messages can still be sent and received in their web interface but your saved messages that you move will be saved locally.

A hybrid of this would be to move folders that you don't really use any more and just have for archival purposes. Whatever it takes to free up space.

The other option of course is to pay them for more storage.