Auth 2.0 Error 400 on Mail account

hello dear apple my ipod device google access denied error 400 error please solve this problem soon thank you

Do you need to delete the old account first? I had the gmail account connected and working, but something happened with google console and my account was locked out. Finally got it cleared and can use gmail through their web interface but can't connect through mail. When I tried to do so using the instructions it gave me an account already exists message. So my assumption is that I need to delete the account from mail and then re-add it. Sound correct? TIA

Wow!! Thank you so much guy! I spent hours for resolving it and then I found your comment.

Just wanted to add that you need to put imap.gmail.com as incoming server and smtp.gmail.com as outgoing server. I have been asked for it, when I logged in as OTHER EMAIL. And then it worked!! Thank you again!

Can confirm that this also worked (5/7/23) on the 2009 Macbook 6,1 running High Sierra. Could only get it to work for one user, however. The option for the two factor authorization was not there for the second user on the same machine and trying to use the OAuth code number of the first user for the second user in MacMail did not work.

Thank you for the post but ...

Wait for it-- drumroll.............

Of course we all saw this coming--

In Google Security there isn't an 'Apps' tab to select-

There is a "Recent Security" section listing your device activities with dates

"How to Sign in to Google" with a list of things like-

2-Step Verification

Password

Google Prompt

2-Step Verification Phones

Recovery Phone

Recovery Email

"Your Devices"

"Third Party Apps with account access"

"Enhanced Safe Browsing For Your Account"

"Signing In to Other Sites"

"Looking For Something Else?"

So which is it?

Unfortunately when I do that (add another account) it says the account already exists. I don’t want to delete the account altogether because I use it on iPhone and iPad and a new iMac. I don’t think there is a real solution for an old iMac running High Sierra/

As of June 18, this still works on High Sierra....the replacement account (from 'other') is really slow compared to the original but it's better than nothing. Thanks to everyone who contributed to solving the issue and creating the workaround.

Hello! I am not jaynemiranda, but maybe I can help, since I had the same problem:

You need to put imap.gmail.com as incoming server and smtp.gmail.com as outgoing server. I have been asked for it, when I logged in as OTHER EMAIL. And then it worked!! Thank you again!

I spoke too soon about it working for me. About 10 minutes after I reconnected after deleting the old gmail account and adding it back through the 'other' option, I got this warning from my mac as a pop up message (i'm assuming after checking for mail via push notifications):

MAIL CANNOT ACCESS YOUR MAILBOX INFORMATION BECAUSE IT'S ALREADY IN USE

Another application on your computer or your local network is using your mailbox information. Click QUIT to quit mail. Then log out of this compute rand any other computer you're using. After you log in again, open Mail on one computer only.

If this message reappears, there may be a network server problem. Contact your system administratro to determine if it can be resolved by rebuilding your mailbox information. Then click Rebuild Mailbox Information.

******

Since my computer is so old there are thousands upon thousands of emails with attachments....rebuilding would take days at the least.

Anyone else get this and how did they handle it?

I'm using the same gmail account on my iphone and also another Mac but I assumed the generated Gmail password would only apply to and affect THIS computer running High Sierra.

Any thoughts? Does this mean I can only have my email running on one computer a time now?

I have tried the steps given by The Animaster and all I get is "unable to verify account name or password"

Background: I changed my google Password as I had an unsolicited verification code sent to my phone

Then my email wouldn't work. I got the same message as others have mentioned:

Authorisation Error

Error 400: invalid_request

You can't sign in to this app because it doesn't comply with Google's OAuth 2.0 policy for keeping apps secure.

You can let the app developer know that this app doesn't comply with one or more Google validation rules.

I have deleted the original Gmail account from my MacBookPro (thank fully it is still all there on my iPhone)

I have tried with and without 2 factor identification on my Google account.

I'm just getting the "unable to verify account name or password" error

I am on High Sierra.

I have 2 other Gmail accounts that still seem to be working OK.

I can access the main Gmail account fine via browser, so I have the correct password.

HELP??!?!? Please

Sorry this isn’t working for you. High Sierra seems to have specific issues of its own. Mine was tested on El Capitan. Sadly, I decided to install High Sierra on my MacBook Pro (I’m that much of a sadist) — knowing full well it would cause my Mac to brick, because the dedicated graphics card was burnt to a crisp (common for the 15” 2011 MacBook Pro) and it was on its last legs with the integrated graphics. In the end I weighed my options — do I continue to work at 1/20th the speed on my old Mac or do I get a new Mac mini and work at the speeds of today… suffice to say it was time to say goodbye to my 12 year old MacBook.

I know this doesn’t help per se, but weigh your options. Because just checking email on my old MacBook Pro became an unbearable task… that was the straw that broke this camel’s back.

Thanks. I’ve got a 2015 Air on Sierra which the same thing has happened but it seems to be allowing me to download Big Sur which is showing as compatible, so I’ll see if I can get that up and running as a temporary measure while I research a new Pro.

Doesn't work for me...and I'm happy to give anyone my phone number. My Account Info window looks nothing like the sample on Google's walk-through at the link. I was already set up for 2-factor ID so I turned it off, turned it back on, but can't see anyplace to reset my PW to the one google generated. So freaking frustrating.

sssllc, where do you go to give IMAP authorization/permission? In my web Gmail, under settings > Forwarding and POP/IMAP, I have IMAP access enabled. Is that what you're referring to?

I tried all the solutions above and they're not working for me, I am a dinosaur running Yosemite 10.10.5 on an iMac 27" Mid 2011. I changed my password and now can't connect my email.

A pesar de haber habilitado la configuración en dos pasos no me aparece "Contraseñas de aplicaciones" sino únicamente "contraseña". Esto me lleva a lo mismo, se abre una ventana para acceder a mi cuenta y poner mi contraseña pero no generar una contraseña. Me puedes ayudar. (te paso captura)

Muchas gracias