Auth 2.0 Error 400 on Mail account

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?

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.

ays177 wrote:

It's not about privacy only. It's about the ultra burden to set it up and make it work . Also no matter what you can't have the imap of Office365, there is not chance as Mail is not compliant to the standard... How something like Apple can get cut out of the main internet feature in 2023? UNBELIEVABLE

The last update to High Sierra was macOS 10.13.6, in July 2018.

Since then, Apple has released five major versions of macOS – Mojave, Catalina, Big Sur, Monterey, and Ventura. Are you claiming that the Mail application in Ventura is not secure enough for Google?

Finally managed to get round this today.

Goto the security option at https://myaccount.google.com

• Enable 2 factor authentication

• Once enabled there is a "App passwords" option on the 2FA page (https://myaccount.google.com/u/8/apppasswords)

• Create an app password for Apple Mail. It will then give you a 16 digit code to use in Apple Mail. (Note that if you copy and paste it will include the spaces between the blocks of 4 digits)

• Use this password in the IMAP/SMTP settings

After that, login to Gmail and goto the pop/imap settings

https://mail.google.com/mail/u/8/#settings/fwdandpop

• Enable IMAP here

Return to Apple Mail

• Sync you email and it should all work fine.

One missing element of the steps outlined in the link is that when you create the App Password, copy it and then go to your Apple Mail app, add account and go to "Other Mail Account" (do not try to add Google Account again or you will continue to get the same message), type in your Google account address and when it asks for a password paste in the App Password that was generated by Google and it will set it up.

edmeyers wrote:

where do i find app passwords.......i'm not seeing it unfortunately but it could be old age

Google Account Help – Sign in with app passwords

You log in to the Google site, and ask Google to create the app password. Then you use it with Mail on the Mac. Note that Google will not generate an app password for you unless you turn on 2-Step Verification.

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.

Brilliant!! It has worked after many days of not being able to.

I think that these security updates that Google makes are for us to update our equipment but not to protect us. I think they are somehow associated with Apple to jointly make profits. They are all the same masters who together manage this entire computer and information business. Some sell programs and computers, others sell our information that they extract from us through their strategies. United for their "business"

This helped, except when I get to the window where I select "other" Google tells me that there is an account with that name already. I was able to use apple mail up until July of this year. Soooo frustrating! And I can't enter a password in the internet accounts window b/c the initial "nope, you can't" message is still there.

Help!

Thank You Animaster. Your solution to get gmail back on Mac Mail worked GREAT! I'm not what I call a computer wizard, but I followed your instructions and it worked. Was ready to buy a new computer as mine is late 2011 but gmail is so painful to use and I have multiple account. But my main one went out. Don't change your password on gmail. That's what caused my main gmail account to go off. Then when I tried to add in mac mail with google it gave me that bs, need Auth 2.0 Error 400. Did't allow me to sync my calendar but just put in under my other gmail account. THANK AGAIN!