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Cannot add/delete Mail accounts nor change/add/...

This has been a maddening 24 hours-- everything works fine for me in Sierra EXCEPT mail (and even it works just fine in the new user I created). I can log into anything I want using Safari. But something dire has obvious gone wrong with Mail.  

In contrast to the new user account, nothing can be changed, corrected, reentered, or deleted and then "saved" and the same wrong configuration reappears when I close and reopen mail, or if I try to change and restart.

I regularly use two different accounts-- and with the new user account I began by configuring one for incoming mail only (pop), and when this worked without problem, I added outgoing mail. And when that worked fine, I added the other account.

Accordingly, for my original user account, I've been hoping today to return mail to its original factory state, and have tried following the advice that seemed to work with earlier OSs-- trashing expired passwords, and trashing the Mail, com.apple.mail, and com.apple.internetaccounts folders, along with half a dozen plist files in Library. (I've never used iCloud). But on restarting nothing changes. And regardless of where I enter what I know to be correct passwords and usernames, I get only as far as "Unable to verify account name or password." (Of course in Mail to save changes the account must first be verified before Mail will shut down.) "Connection Doctor" is much the same story, with the error message: "Trying to log in to this POP account failed. Verify that the username and password are correct."  A similar result  happens too if I try to use Systems Preferences Internet Accounts to create a brand new account of any kind, even if totally unrelated to the two I've long used in Mail.

And, finally, just to add to my complete bafflement, for about ten minutes, even with several error windows on display, and remaining so for half an hour, Mail suddenly connected to the incoming POP mail server and downloaded a dozen messages, and then even allowed me to send a single test message out. 

Again, nothing I currently have in mail needs to be saved, and I'd like to nuke it back to a fresh, preference free state with nothing entered. Or do anything else that won't be a second fresh install. (I do have another MacBook Pro running Mavericks where everything Mail works fine). 

You accidentally deleted some mail plist from user library and that is to be avoided , when a new user account is created and mail application is configured mails will start downloading from the server .

But for safety reason mails can be stored in USB  stick I answered to a thread Mail.app not working. Need to backup before reinstalling.

And this method that works for me as I have applied in my system many times if mail application is corrupted .

• Take back of all mails in V4 folder : Method to copy mails in V4 folder .

Click on Go on top menu bar , hold option key click on  > library > select mail folder  > right click on mail folder there itself  > click on copy mail > right click on extreme right hand side in column B , that is below persistence info.plist > click on paste item .

Entire mails are copied to V4 folder .

Go to the corrupted IMAP account > open its preferences > select Accounts  > select the account that has to be deleted & click on minus sign .

Configure new IMAP account , go to top menu bar , file > import mail boxes > import data from > select apple mail > click on continue > select the back drop folder then choose new .

When new IMAP account is opened , a new folder with all mails will appear in the mail side bar .You can rename the folder .

I am grateful for you suggestion-- but my problem is not how to back up my mail, it's NOT being able to delete the presumably corrupt account in the first place (which is POP) (I have never had an IMAP account on this computer). And this was the case for 14 hours before I tried to delete mail plist and various other files and folders (all of

which I actually have saved).

Which mail plist you tried to delete from user library and what is the name of that folder , is that plist on the desktop or in trash , or have you emptied the trash so that plist is deleted forever and what folders are you stating and where are they saved .

Some information is required .

Again, many thanks indeed for your response. But what I want to do is start from scratch, purge all my internet accounts, and all  my internet connection information, and begin again. I cannot however (not via mail nor using internet accounts in system preferences) either to add or delete. And the error window (that a +account cannot be "verified") is almost instant-- suggesting the problem is in what is being sent out or how (since using Safari to access these accounts is fine).

Trashing various files (copied to an external drive) then put in trash, emptied, and then rebooting changed nothing whatsoever for good or bad, and all same old configuration info and log-ins appear. Nothing new entered can be saved because it cannot be authenticated, so I am stuck in an infinite loop.

With a different new user account however everything is fine. But on my old account all the various front end ways to purge accounts or alter their individual configurations fail, or add new accounts fail.

As for trashing library files, it was my Mail folder and com.apple.mail folder; com.apple.mail-shared.plist in versions dated during the past 48 hours; and a com.apple.mail.plist.lockfile from 72 hours ago.

I don't want to switch back and forth between two users if I can figure out a way to get the non-working one to work. A fresh install of Sierra is as unattractive an option as returning to my last stable clone of El Capitan.

The method that I posted is a manual method to copy paste each mail that is stored in user library > mail > V4 folder , the entire mail data is stored in V4 folder , once new mail account is created the V4 folder data is exported to the new mail account .

But , unfortunately and unknowingly some important mail plist and files are deleted in that case .

You have to switch to new user account in your system How to test an issue in another user account on your Mac - Apple Support

Mail for Mac: Set up Mail with your email accounts

最后更新：2017-09-16 16:34:31

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