I have a GMail account, and I access it from two Macs, and an iPhone. The iPhone and one of the Macs (10.14.x) still works.

On the other Mac (10.13.6), it stopped being able to receive mail a couple days ago. The "Mail Connection Doctor" says "Trying to log in to this IMAP account failed. Verify that the username and password are correct", and likewise for SMTP.

I found some ideas online and tried them, but nothing so far has worked:

  1. Go to https://myaccount.google.com and turn on "less secure account access" (it was already on)
  2. Go to https://accounts.google.com/b/0/DisplayUnlockCaptcha

I haven't changed my password in the past month, and I can still log in to GMail with a web browser.

When I go to "Accounts" in Mail.app and click my GMail account, it presents an OAuth-like sheet asking for my Google email/password. When I complete the form, the sheet turns gray (empty), and only the "Cancel" button remains.

I found reports that GMail broke on Mojave recently, but my pre-Mojave system is the one that broke.

Any ideas for how to make this work again?

UPDATE: I've been clicking "Check Again" several times, and one time I got IMAP (only) to work, and it downloaded this week's email, but then it stopped working immediately. I don't think I was doing anything special that time.

In the "Detail", I see:

250-smtp.gmail.com at your service, [my.ip.address]
{many more 250-prefixed lines}
334 VXNlcm5hbWU6
{my b64-encoded email}
334 UGFzc3dvcmQ6
501 5.5.2 Cannot Decode response {big_ugly_code} - gsmtp

That's not my password -- it really just says * there (though I don't know if Mail.app substitutes that in the window for safety).

UPDATE 2: Calendar.app has all my latest calendars, for this same Google account, and syncs fine on this computer (though obviously not with SMTP or IMAP).

  • 1
    I would suggest deleting then recreating that account from scratch.
    – IconDaemon
    Commented Apr 9, 2019 at 18:10
  • IconDaemon: Sounds like a plan. What are the consequences of that? Will it just wipe out the local copy, and re-download it all? Will all my drafts be here when I re-add it?
    – NoMail
    Commented Apr 9, 2019 at 20:36
  • This page at Apple support will answer your questions. Make sure you understand how to save content from Mail on your Mac before you delete the account. If you have set up Mail to always delete from the server, (thus making your only copy of the messages on your Mac,) this is especially important. In this case, you will also have a backup of the Mail content in Time Machine. You do run Time Machine, yes?
    – IconDaemon
    Commented Apr 10, 2019 at 11:12

1 Answer 1


Do you have your account configured with your regular GMail account password or an "App Password"? Do you have two-factor authentication turned on?

I've had my home cameras configured for several years to send me emails via SMTP using my GMail with an App Password to email me if any motion is detected. I usually get several emails a day but this week suddenly it stopped working. I generated a new Google App Password and even disabled 2-factor authentication but I still can't send any emails from my cameras. Again... this has worked flawlessly for 2-3 years with no recent changes to my camera.

I encountered someone else having similar issues here: https://www.cnet.com/forums/discussions/outlook-365-no-longer-connects-to-gmail-smtp/

I'm thinking google must have changed something.

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