hotbaba Said:
"Thanks for responding, but... surprise Mail was NOT a login item. Any further thoughts?"
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Two Thoughts:
A. Try Adding Mail to your Login Items:
- Go to: System Preferences > Users & Groups > User Name > Login Items
- Click: the “+“ button
- Select: an Mail
- Click: Add button
- Try logging out, then back in.
B. Elsewise, it seems the Mail app is corrupt.
Request Instructions from Apple: Researching this it seems you need to rebuild the Mail Index. Contact Apple Support, asking which files to delete, and how so. How to Reset It:
- Move: a few folders (not their internal files) into Trash
- log: out
- log: back in
- try this once more
Apple Support Contact Info:
Note: Phone calls are taking a bit to go through at the moment, due to lots of calls. With the Coronavirus Pandemic, many are at home at the moment, with much time on their hands to contact Apple. So, just stay on the line, and you will get through :)