My mail keeps crashing for no reason

Jim Stewart Said:

"mail: I am running High Sierra on iMac (11.2) and Mail keeps crashing for no reason that I can identify.[...] I reinstalled the Security Update [...] but the crashes keep happening...."

-------

Five Thoughts:

Seems something is misconfigured here. So, try the following.

I. Reset the SMC and NVRAM:

Sometimes changes are made to the system(i.e. updates) and then settings (i.e. for Apps) become manipulated, technically. So, reset both on your Mac:

II. Clear your Temporary Internet Files (Cookies & Cache) of Safari:

• Cookies perform remembrance of certain site-entered data.
• Cache keeps a snapshot of the last time you visited a site.

Use this Link: Clearing History and Cache - Apple Communities

III. Use MalwareBytes for Mac:

This is software that searches for malware/adware. So, scan with it and then remove what is found. Once removed, uninstall MalwareBytes for Mac. Then restart the Mac. It is created by longtime users of these forums. So, that is why it is the only way to go about securing your Mac, when it comes through use of software 

Downloads:

1. Malwarebytes Anti-Malware for Mac
2. Malwarebytes uninstaller

IV. Any Security Software Installed?:

• Security Software's firewall settings would want to make sure that you are getting secure accessibility to your Mac. So, connecting to sites might not be an option, if firewall settings are part of it and enabled.

• Uninstall it, using the uninstaller from the developer’s site. Just dragging a dropping its icon into the Trash will undesirably leave caches and other files sitting around on your Mac. So, use the uninstaller, contacting the developer of the software of where to get it on their domain.

V. Create a New Administrator User:

Are you logged in as an Administrator? Create a new Administrator user, and see if this still occurs while you are logged into a different Administrator user. If not, then it is something configured in your current user. So, from there, delete the current user and then just use this new administrator account. You would move all of your files over to this newly-created Administrator . See if that fixes it.

Hello and welcome to Apple Support Communities, Jim!

I understand you're having trouble opening the Mail app on your iMac. I'd be happy to provide information to help you troubleshoot this.

Before opening the app, press Shift on your keyboard and at the same time click the Mail app. The app should open correctly. If not, try opening it in safe mode: How to use safe mode on your Mac

If it opens correctly there, restart your iMac and test to see if it opens correctly when booting up as normal.

Let us know the results.

Have a great day!

I would check to see if your system has Security Update 2020-002 High Sierra installed. It addresses a number of vulnerabilities in Mail. If it is showing installed, you may want to try to reinstall it or reinstall MacOS High Sierra 10.13.6. I have a similar issue with my system where Safari is doing the same thing so I am reinstalling the same security update.

Hi Jim, try this...

https://discussions.apple.com/thread/251262292?answerId=252503609022#252503609022