Syncing mail between multiple computers

The origin of the broken email synching between machines in El Capitan (and Sierra) is that Apple Mail cleverly started building a deep hierarchy of folders within ~/Library/Mail/, where the email is stored, and at one level a common folder name is defined as a long hex string that is likely based on the hardware address of the Mac one is running on. Therefore any conventional attempts (e.g. using Dropbox, or an app like ChronoSync) to sync between two Macs break because this hex string is different on the two Macs. It is a pain in the neck but I presume the Mail author(s) decided this change was critical for some arcane reason. Maybe its critical for icloud usage or something. Personally I just gave up on Apple Mail because of this. (Both Airmail and Postbox, for example, remain more conventional in their file naming and conventional synching is possible between machines, although they store emails in database files which can be pretty large and they're the objects which have to get synched.)

I'm struggling with this issue also.

I travel only rarely, but when I do, I want to take my entire MAIL folder including all history with me.

In the past this was easy: I just copied Library/Mail to the same location on my MacBook. Worked fine.

Since El Capitan this does not work anymore and I'm stuck with no solution.

I do not want to change my email accounts, some are IMAP and some are POP.

Does any body has an idea?

This problem cannot be that rare.

The problem isn't as rare at all. Most of us have given up to get it working when nothing will fix it, not 3rd party utilities nor any clever workarounds or home-brewed scripting hacks. Personally I think it's just to much PITA to deal with and just going to check mail using a web client (gmail's own client for instance) is a far easier way to do. Eventually one gets tired enough to slam his head against a wall and will naturally follow the path of least resistance. I would most definitely advise to use webmail especially with gmail whenever possible as it's unlikely such "client" would change to the point one will need to look for workarounds. The only issue might be if needing to access email offline, but then in such case one could use other clients like thunderbird, airmail, postbox, etc. and see what best works for you. Until such feature would be natively supported by apple mail, I've given up complaining or trying to request it. But hopefully one day it will become evident that many users have multiple computers and devices as well as multiple email addresses and perhaps Apple Mail will allow to natively support sync across such multiple devices. For instance it would be great if a form of "lazy loading" was possible where depending on a search term or a given scrolling view mail would be retrieved real time from the IMAP server with no need to store anything locally unless users would mark a message, sender, or mailbox to be made available for offline access. One can still hope right? 😉 By the way should any of you find an effective workaround providing a solution (even a fairly convoluted one) please do share it here... it would be very welcome. Cheers and thanks for the info posted above! 🙂

POP accounts are not designed for syncing between devices and is a pain to try doing that. Eventually, something will get corrupt trying to sync messages between devices.

Are you sure you can't convert those POP accounts to IMAP? A simple solution for POP accounts is to use webmail for those accounts.

IMAP is not broken. Use IMAP to sync email accounts across multiple devices. IMAP is designed to do exactly that. POP is not designed for syncing email across devices. If anything, using some third party app to try to force POP to do something it is not designed to do is complicating things.

As Bob says, IMAP works fine in Mail. Some people have problems with certain providers, but most work just fine. If you want to list your POP account providers, maybe someone here can give you some insight to whether or not it works well in the Mail application.

I didn't say it was not possible to sync POP like you are doing. I said at some point it would probably cause corruption and problems with what you are doing. I don't know what OS you were using before, but Mail works about the same for several OS back. A few things changed like the storage folder changed from V2 to the V3 folder from Yosemite to El Capitan. Structure remains about the same.

I would suspect that Chronosync may need updating. I've never used it or know what it does exactly, but you may want to check with them. If you have to choose the folders to sync, I suggest you verify the path to the mail location. As I said, the major change is that mail was moved from the V2 folder to the V3 folder. This might be as simple as you making the adjustments there in Chronosync.

The correct path to mail is ~/Library/Mail/V3.

Do I think it should work. Probably yes, but I have no way to test it with POP accounts and I only have one computer. Make sure both computers are running the same OS.

Is this a good idea? No. You run the risk of file corruption doing this. And syncing corrupt files from one computer to the other will then transfer the corruption to it also. Glad it worked out for that long. Computer OS keeps changing and if you can get it to work today, will it work tomorrow or after the next upgrade. Mail is pulling other info out of the database and it may be getting corrupted. You might try re-indexing Mail on one computer then try syncing to the other.

Nothing has changed as far as folder structure except for the V3 location. The mail file format are still the same and no other files are changed in the MailData folder. Restoring the V3 folder from one computer to the other should work the same.

You never really said exactly what was the outcome of trying to sync. Is Mail working OK other than sync.

What you should do is verify on both computers that Mail is functioning OK as separate devices. If not, then fix the issues on whichever one is not right. If one computer is having corruption problems with Mail, then it might affect the syncing issue.

On the chance that there are no issues with the computers, then it's up to Chronosync to make a version compatible with El Capitan. Did they say it was? If they offered a beta version for you to test, then maybe they know there is a problem.

If you want to test it manually, then manually transfer the contents of the V3 folder from one computer to the other. Then open Mail on the other computer and see if it works. That should tell you if it's a Chronosync problem or not.

Most people who want to sync their mail between devices use IMAP, or just set the computer to leave the message on the server when using POP so other devices to download. I think what you are doing as far as trying to do an exact sync is very rare. People have discovered IMAP which does exactly what you are trying to do. So why bother with Chronosync when IMAP will do that immediately with no extra steps. Of course I understand that if your provider doesn't offer IMAP, then that's a different story.

And if you ever throw a phone into the mix, then Chronosync will probably not do you any good.

I think overall it would be the best decision and easiest way overall.

If you do more testing with this or find the problem, post back the results. As I said, it probably should work if Mail is not having other problems, and a manual test should verify that.

It really isn't a question of whether or not replacing the files will work, as I know it will from backups of the same drive. It's moving the files between different computers that provides the doubt on consistency, especially when doing that over and over.

Good Luck

While II haven't tried this with Apple Mail - I use it to keep my documents / desktop / music / downloads in sync between multiple laptops...

Have you tried a combo of symbolic links and Dropbox for this? Set a symbolic link for your Apple Mail directory to Dropbox (or Box, etc.) on each of your machines. Let Dropbox or Box do the work of keeping everything in sync for you. My guess would be as discussed earlier the risk of corruption if you have multiple devices open simultaneously writing to this folder, but you seem pretty disciplined about this with CS. Dropbox would notify you of a "conflicted copy" but that might be pretty ugly with Mail. It works fantastic for the other folders above just haven't tried it with Apple Mail.