Mail toolbar keeps resetting itself

Have you tried restarting?

I'm not sure which file stores this preference, but it's most likely in one of these files in your User's Library.

• Containers > com.apple.mail
• Preferences > com.apple.mail.plist

Drag to Trash

Restart

Make sure to empty trash BEFORE you open Mail.

Reset your preferences in Mail. Do they stick now?

Users sending feedback need to include full details of their hardware.

BugReporter http://bugreporter.apple.com

Free ADC (Apple Developer Connection) account needed for BugReporter. Setup a free account

http://developer.apple.com/programs/register/

Mac OS X Feedback (no account needed)

https://www.apple.com/feedback/macos.html

I don't normally recommend users sign up for beta program but in this case the detailed feedback app includes reports from Console that could help Apple fix this problem. You can always leave the beta at any time. There is no Apple Public Beta forum to discuss and get help. MacRumorsdoes have a place to get help but it's all volunteer.

AppleConnect Sign In

I've deleted those files, rebooted the computer and even formatted and installed from USB. I still have the same problem.

Either the folders I put in the favourites bar reset to the default "Inbox, Sent, Flagged" or the toolbar resets itself to "Icon and Text". Finally in settings I usually remove the option to Increase Quote Level. But whenever the UI resets, this setting also resets.

Could you test in a new User?

Testing in a new User will quickly tell you if the problem is system wide or if it's your User's folder that contains the problem.

CREATE A NEW USER

Go to System Preferences --> Create a New User in Users & Groups.

Switch to the New User by logging out/in or use Fast User Switching.

You can skip logging in with an Apple ID unless you need to test iCloud. Hit continue then skip.

(I suggest checking only Mail in iCloud for this test if you have an iCloud email account)

Only default Apple apps will be in the Dock in the new User. Go to Applications to open other apps you might want to test.

Open Mail,

Customize the toolbar and add to favorites.

Do you still see the issue?

If yes, then the problem is with your base files or it could be hardware related.

If no, then the problem is in your User's folder.

This problem is occurring on several machines including one that was completely wiped and had a clean install of macOS10.13.1. It is also being reported elsewhere. Furthermore it is Mail and only Mail that is affected, all other aspects of the machines run perfectly.

For those reasons, I am fairy certain it is a bug in macOS and nothing to do with User's folder issues.

I have the high-end 2016 MacBook Pro 15” with Touch Bar, with the 4Gb Graphics upgrade and 1Tb SSD upgrade.

This problem existed in the beta version of High Sierra and I reported it to Apple, but unfnothing came out of it.

In fact, Onyx.app doesn't resolve the issue. It's still here some days after.

But when the problem reappears, I restart Mail.app one or two times and my preferences are back. So it looks like sometimes the app just doesn't find the right preference file or something like this.

I seems that the problem is being reported in other places. If you are having problems with Mail please report it to Apple here:

Feedback - Mail - Apple

Just found an additional way to send details to Apple.

How to attach a sysdiagnose to send Bug Report

Have now sent full report to Apple via the ADC. Lets hope they get onto this quickly.

John

Had the same bug. Running Onyx.app (Automation tab with all checked) seems to resolve this.

Always do a backup before running Onyx…

Unfortunately running Onyx appears to resolve the problem only briefly, then it returns.