Apple Mail has simply stopped working. I was on with Apple tech support yesterday for a while. We restarted the iMac in safe mode, but that didn't fix the problem, nor did anything else work. The upshot is that I might need to reinstall the OS to maybe get Mail to work again. I do not want to upgrade to another OS because the programs I use may not work on them except maybe, possibly Sierra. At one point today I was able to open Mail by clicking on a saved message, but then it crashed again. The icon in the dock has a grey circle with a black dot in it at the bottom right of the icon instead of a black dot beneath it. Does that tell you anything except that there's a problem? I never discussed this with Apple, but is there any chance that deleting a .plist file for Mail might fix it? What do you think the chances are that reinstalling the OS will get Mail back? What unintended consequences might/will there be? I have Time Machine as my backup. I am not totally without mail since I can get and send it through Earthlink's WebMail, but it's clunky, and I can't save messages from it to my hard drive unless I do a screen save. There's no drag and drop in it. This newbie to the Forum thanks you in advance for any suggestions or comments.