Auth 2.0 Error 400 on Mail account

Hi Guys, I managed to solve everything!

I have Macbook Pro 2011, Hig Sierra.

My steps were as follows:

1) I left the old gmail account disabled which didn't work.

2) Thanks to the system indicated above I logged into my Google account and created a new password for MAC and Mail.

3) On the Mac, in the mail app I created a new account by choosing "other" and writing my email with a dot before the @ (example: mymail.@gmail.com)

4) At this point I verified that the new account was working properly.

5) I re-enabled the old GMAIL account which no longer worked and... as if by magic it started working again!

6) At this point I deleted the new account I had created thanks to the "others" function

The old GMAIL account works fine!!

[Edited by Moderator]

Your solution was VERY helpful. I recently upgraded form OSX10.11 to 10.13 and was hit with the OAuth 2.0 Error

a small additional step to your #3.)step: after Enabling 2-step verification, the "App Passwords" did not show up on the "Signing in to Google" page. Instead, I had to click the right arrow at the far right side of the “2-Step Verification” line. That brought up a page titled "2-Step Verification" at the very bottom of THAT page is “App Passwords”

The solution by "the Animaster" works. I have High Sierra on a 2020 Macbook. Pro. You need to follow Animaster's directions carefully. In step 4, copy the new password, but then ignore Google's on-screen instructions, and follow what it says in steps 4 and 5. However, if you do not remove the old instance in your Mac mail account list, it will say there is already an account with the same name, and it won't let you create a new one. Delete the old one. It does not get rid of all your emails. Choose "other", using the same email name as you had before, and the new password that you get in step 4. Then it works, and the old emails are still there (including those that came in while it wasn't working).

This solution actually worked, THANK YOU!

As of 4.12.23, there are a few more steps to get to the app passwords now. AND you must go into your Gmail settings and go to "permissions" to make sure you have IMAP authorized/give permission. If you miss that second step it won't authorize. This solution remedies the need to give google your phone number (yay!).

Stick with it, guys because I am not super techy and if I can do it, I am confident that you all can do it, too! Good luck!!

Thx! I managed to get access to my G mail on my mail using the the process all OK and good but did hit issues as the g mail on my phone then wouldnt accept the Pwd and had to try and change it via g mail. Did so but kicked me out of Mac Mail. Was like vicious tech circle. Seems cant operate g mail using the 'other e mail acct' both on mac mail and also on my phone.

In the end i went for less pain and updated my Mac to OS to Monterrey. Was able to transfer g mails to may mac no problem. Cheers!

Was the same for me, I did it and it works perfectly. When you start a new account settings, don't do it by google... do it by the option "other account" and work as they said. Hope this will helpful

try searching for "app password" on your google site. I had the same problem and needed two additional steps as I explained above.

Answer for Mail and Calendar is here: Calendar and Google's OAuth 2.0 policy - Apple Community

Hey, I was able to

reinstate my other half’s gmail on his apple account on his iPhone by removing the 2 step verification in Gmail settings. We can’t seem to sort it on our old MacBook Pro. Good luck!

Animaster's advice is very helpful, but I needed to make two changes since the OP. First, the App Password did not automatically appear as an option on my Security Page unless I typed App Password in the search field. I also had to take one extra step in between 4 and 5, then it worked. While still in your Google account security page, under Recent Security Activity, open "App password created" and authorize the change. Then you can proceed with step 5 above.

For what it's worth, I was able to get it to work by downloading the Chrome browser and setting it as my default browser. Once done, try to log into your Google account like normal. Once all is up and running, you can change your default browser back to Safari. Much easier than setting 'app passwords' like Google is trying to make us do.

I could not, for the life of me, figure this out. The proposed solution still didn't work for me, but...

I found a solve

I noticed that the popup to login into google, when trying to add a new account, was opening in Safari Private Browsing mode. I went digging in Safari's settings, and in the "Advanced" tab under privacy I turned off the "Use advanced tracking and fingerprinting protection" AND the "Allow privacy-preserving measurement of ad effectiveness" and BAM... I was finally able to get past the 400 error that Google was sending back and I was able to authenticate and add my Gmail account to my Internet Accounts.

Hope this helps others.

Spoke with Apple tech and solution takes about 15 seconds:

1. System settings
2. Go to: Desktop and Dock
3. Go to: Widgets. (Honest)
4. Go to: Default web browser
5. Change to Google Chrome

That should download all emails and google calendar.

Had that problem, too. Drove me NUTS! You have to scroll to "Add Other Account" ad then select "Mail account." It's maddening. Still trying to re-synch my calendar.

Hello guys,

I found the solution for the calendar... I mean something very similar.

Just download 'One Calednar" on your mac. It is free and in 2 minutes I as able to connect all my Gmail accounts.

The design is a bit different but it makes the job perfectly.

Best of luck.

C.