Q: macOS Sierra - Apple Mail - can't access Gmail

Yep. No Gmail since upgrade. Sad, very sad.

Remove the Gmail account in Mail by clicking on the "-" sign in Account.

This will take you to System Preferences > Internet Accounts

Remove Gmail in Internet Account. (not just uncheck Mail but remove the account)

With Mail quit....

• Go to the User's Library folder. (see below)
• Scroll to Containers
• Delete the com.apple.mail folder
• Scroll to Mail folder

             Inside the V4 folder you'll find several folders with names like this:

Open each folder and find the folder that contains your Gmail account. Delete the entire folder.

• Open Keychain Access in Applications/Utilities.
• Find your Gmail account. There could be more than one entry.
• Delete all entries.

• Log out under the Apple in the Menu bar.
• Log in
• Open System Preferences > Internet Accounts, Add the Gmail account. If you have two step authentication enabled you'll need an app specific password. https://www.google.com/landing/2step/
• Open Mail
• Under Window in the Menu bar, open Connection Doctor. Do you see green icons for Gmail account?

Show User's Library

The User's Library folder is hidden by default. To unhide: Select the Finder in the Dock. Under Go in the Menu bar > hold down the Option key and you’ll see the Library.

Finding the User Library Folder

http://www.takecontrolbooks.com/resources/0167/site/chap11.html#FindingtheUserLi braryFolder

Holy $hit. I have five Gmail accounts. I did not sign up for this.

You can always use your web browser to view your Gmail account.

Ummm... apple mail is supposed to accept Imap accounts. I have never had to delete an account and recreate with an OS update. I have reviewed your posted instructions and unfortunately all five of my gmail accounts in the mail folder are identified with "gmail," no other account identifiers.

I will use my iOS devices to check my mail until there is a fix for this.

Thanks for the instructions.

There was an upgrade in Mail from either V2 or V3 to V4. This process failed for some users. No update is going to fix this.

I expect there to be 5 folders for your 5 Gmail accounts. If you see a 6th folder it will have Outbox in this and any local custom folders you have created.

I just got off of the phone with apple support. They said I must have changed my pw when upgrading, but I did not.

Anyway, they had me boot in safe mode, delete my apple account info and keychain on my mac, reboot, reboot, and recreate my iCloud info, then go back into mail (this is not an exact description of what we did, as I don't remember all the steps or order of them, so don't try this at home). After all that, when I entered the userid and pw, mail responded and my accounts were okay again.

I suggest you contact them via twitter @applesupport. That is how I resolved this. Thanks to great support from apple.

I switched from PC to Mac about two and a half years ago and in the last year, I'm starting to wonder why. Mail and calendar apps are not user friendly and do not have the functionality of Outlook. My MAC-version Microsoft apps don't behave as well and it has taken me several tries to change my apple ID.

Today, I get home to an update and now I have to try to reconfigure my 4 gmail accounts? Honestly, feeling it's time to go back to PC.

It's best for most users to wait to upgrade to a new macOS/OS X after it has matured. There are always issues with the initial releases. Wait until .4 or .5 in the future before upgrading.

Here is what worked for me:

1. While in mail go to Preferences

2. In the preferences window go to "Accounts"

3. Click on the account that will not connect post the upgrade (haha - ya upgrade, I know it worked before!)

4. Click the "-" sign in the bottom left (like you are deleting the account)

5. A window will pop up "You can remove this account from iCloud in Internet Accounts."

6. Click the button on the right "INTERNET ACCOUNT"

7. You will be prompted for the password for the account and it goes right back online.

I hope this helps you too.

Fantastic answer; this is the one that worked for me!

I don't see the "-" sign bottom left.......

Zhivago, look for the + - on that screen, used for adding or deleting an account.