Gmail stopped working on my MacBookPro, can't sign in using Mail App; Same issue with Comcast

iOS doesnt' run on MacBook Pros.

MacOS runs on MacBook Pros.

Go to Apple menu -> About This Mac, and confirm you are running El Capitan.

Then try to access your Comcast and Gmail acconts on a compatible web browswer with your operating system:

Browsers by Mac operating system - Apple Community

Get the IMAP settings, and use add other... when creating a new account on Mac OS X Mail following the IMAP settings. The prepopulated Gmail settings, that came with that old Mac OS X probably don't work anymore. IMAP though works back to many more older operating systems.

There are many other threads here about the same issue. Google tightened up their security requirements, so they now won't let "less secure" applications (like the versions of Mail in old versions of macOS) connect to their system unless you turn on Google's version of two-factor authentication, and use an "app password".

(Google generates the "app password" for you, then you use that with your "less secure" Mail application (the one on the older Mac) to let it connect to the Google servers as an exception to the tightened security rules.)

Here's one of the many Apple Discussion threads about it, and the link to the relevant GMail Help page.

Auth 2.0 Error 400 on Mail account - Apple Community

https://support.google.com/mail/answer/185833?hl=en-GB

PhotoGirly wrote:

Is this Apple's way of saying my old faithful MBP (iOS 10.11.6) is faithful no more?!

Get a new laptop?!

Ideas?

TIA

Apple hasn't done anything to break Mail on El Capitan (10.11.6). They also haven't done anything to update El Capitan since July 18, 2016. Any security update to Mail would have been in newer versions of macOS - Sierra, High Sierra, Mojave, Catalina, Big Sur, Monterey, Ventura, and soon, Sonoma.

It sounds to me like setting up your Mail account again, with the "app password", might work for the time being. (Until Google decides that they no longer want to support "less secure" mail applications even if you use one of those passwords.)

What MacBook Pro do you have? (Model description, including hardware model year, from About This Mac in the Apple () menu. Please do not post your machine's serial number.)

Your Mac is clearly old enough that it can't run Ventura, but you might be able to run something a bit newer. Even just a one- or two- version upgrade (to Sierra or High Sierra) might be useful in some ways. For example, although the main version of Firefox now requires Catalina or better, there is an Extended Service Release version which will run on Sierra / High Sierra / Mojave, and will probably still get critical security updates until September 2024.

Having Firefox (as well as Safari) might help if you are running into some Web sites that old versions of Safari can't display correctly, or if you are running into banking Web sites that complain that the old versions aren't supported.

I have been having the same issue and as I do not want to update my computer and lose useful applications I need everyday, I have chosen to switch from mac mail to Thunderbird & it works fine.

If you need different emails make sure you make a hint list, never hint your whole password, just a portion of it, as a reminder.