I think all the folks suggesting that we uncheck the box to "store messages on the server" are missing the overall point. Yes this a workaround that might work, and as someone has already pointed out, it's an OK solution if you want to store sent mail on your computer and not on the server, but it dodges the original problem and creates a whole new one. I don't want to store sent mail on my computer! I want to store it on the server like I always have with every mail program I have ever used until now – most recently, with Microsoft Outlook for 10 years with no problems whatsoever before I switched, like an idiot, to Mac Mail at the beginning of this year. If you use a different computer at your office than you do at home, as most of us do, or if you use different devices to send email period, as most of us do, then not storing sent mail on the server is going to be a big problem at some point. You are going to find this out sooner or later when you need to find an important email you sent and realize it's on the office computer, or the home computer, or the laptop, or wherever, but it's not where you happen to be at that moment. The bigger point, though, is that this should not be an issue at all and Apple should figure out what is causing it and just fix it already.
So, I tried the idea TanjaJ suggests above to create a rule. I did this for both of the email accounts I have under my mailbox, and set up a rule to send all outgoing mail for both accounts to the Sent folder. I had high hopes that even though this solution, if it were to work, would again be fixing a symptom and not addressing the actual problem (something only Apple can do), it nevertheless might at least keep me sane for the time being. But, alas, it did not work. I lost an email I sent yesterday and I lost another one just a few minutes before I started typing this post. It usually doesn't happen that frequently. And again, the lost emails had nothing in common so there's no common characteristic that I can see causing it to happen. The problem continues. I think I'm done with this miserable Mac Mail experiment. It's 2015, for crying out loud, and people who spend as much money on Apple products as I have (almost $3K for a friggin Macbook Pro!) have a right to expect better. I haven't been very impressed with Apple lately – at all. It looks like they are putting all their attention into making wristwatches while forgetting about those of us who use their products ever day to do important things – like trying to make a living.
I don't know. Maybe I'm being too harsh, because I know that sometimes change takes time. Look at Safari, for instance. I've been using that program since its inception (I told you I was long-time Apple user – much longer than that, actually), and Safari definitely has had its ups and downs. But after a lot of trial and error I think Safari today is one of, if not the, best browsers out there. So it can be done. This problem with Mac Mail seems pretty clear cut. As others have noted on some of the 43 pages and three years of posts here in this thread, it seems as if there's a hitch between the time when Mac Mail actually sends the email and it gets saved to the outgoing server. Regardless of what is causing the hitch, a network timeout or whatever, it ought to be something that Apple can fix rather easily. After all, other email programs don't seem to have the issue. All it would seem to take is for Apple to adjust the program so that instead of discarding the sent mail when it gets a timeout from the server, it holds onto it and tries again to save it a few minutes later. It can't be that hard. If I were in charge at Apple, I would clean house in the Mac Mail department and start over. The whole program is boring and lifeless, not to even mention its basic functionality problems. Come on Apple. For pete's sake get this program right or this will be last post I make before going through the huge inconvenience of switching email programs yet again.
