I need to update my email signature on Mac Mail (currently on MacOS Mojave).
When I select "Preferences / Signatures" in Mail, the pop up box is just grey, with no signature options. In fact, no other options in Preferences are appearing - it's "stuck" on a grey signature box!
Always advised to have a current backup before proceeding— in this way you can always restore to a previous state if somrthing goes astray.
Quit mail.
Finder>Go>Go to Folder, copy & Paste:
~/Library/Containers/com.apple.mail
Highlight all the contents in this folder
Then right-click and choose "New Folder with Selection”. Do not move the new folder from this current location.
You can close the Finder window.
The next step will be to restart the Mac and test
After the computer is restarted, open the Mail Preferences to see if it opens properly.