Apple Mail won't accept my gmail password

Yes, I solved. 2-Step verification solves. After 2-step verification you have to generate specific app password for email app into Google usually for mail are 16 letters.

You can create second Google app password even to synchronize contacts

i confirm it works, however u must also set that password for smtp, that wont save in the first window (a bug?). u have to enter smtp server list and change it from there

Sign in using app passwords

An app password is a 16-digit passcode that gives a non-Google app or device permission to access your Google Account. App passwords can only be used with accounts that have 2-Step Verification turned on.

About POP--as far as I can tell, neither 2-step verification nor using an "app password" will fix this. At least it didn't help in my situation. I tried both of those, I deleted keychains, I restarted, I deleted and re-created the accounts. If I created an account using IMAP, it works; if I created it using POP, it would *not* verify the password. Ever. I wasted the better part of a day fighting with it. I guess I have to try to get used to using IMAP.

My Mail app is set up to use Gmail via POP. After turning two-step verification ON in my Google account and creating an app password as indicated above this solved the problem. I don't like IMAP, and would have changed email provider rather than use it.

I had this issue also. What fixed it for me was generating a new app password and putting it in both incoming and outgoing password fields in Mail account preferences.

The issue comes from Google:

Less secure apps & your Google Account

To help keep your account secure, from May 30, 2022, ​​Google no longer supports the use of third-party apps or devices which ask you to sign in to your Google Account using only your username and password.

Important: This deadline does not apply to Google Workspace or Google Cloud Identity customers. The enforcement date for these customers will be announced on the Workspace blog at a later date.

For more information, continue to read.

https://support.google.com/accounts/answer/6010255

My Mac is running Mojave OS (10.14.6) and Mail (12.4) but as of today can no longer send nor receive messages. Mac Mail prompts me for a password, but then tells me it was unable to be verified.

Mazolla Thunderbird

Thunderbird

Well, I'm glad I'm not the only one who doesn't like imap! Maybe someone will come up with a solution, I hope! Do you know of an email client which supports POP? Although it seems to me problem is with Google, not Apple. I'd be glad to be wrong there, too.

You are welcome and thank you too.

Do come back to the Apple Support Communities ( ASC )  in the future, if / or when additional questions may arise

Thank you for posting this solution!

Good Work there 👍

Will book mark for future reference to others with similar issue.

So to keep pop3 protocol I have to set 2-Step Verification on google account ?

seriously? no way to fix it? i hate imap. ill use another mail app rather than use imap...