Apple Mail not marking messages as Read, after opening an viewing. Also does not delete nor move to trash, but does change Delete icon to Undelete.

Give this a try: boot into Safe Mode according to How to use safe mode on your Mac and test to see if the problem persists. Reboot normally and test again.

NOTE: Safe Mode boot can take up to 3 - 5 minutes as it's doing the following; 

• Verifies your startup disk and attempts to repair directory issues, if needed

• Loads only required kernel extensions (prevents 3rd party kernel/extensions from loading)

• Prevents Startup Items and Login Items from opening automatically

• Disables user-installed fonts 

• Deletes font caches, kernel cache, and other system cache files

VinRaiaJr,

Please start your Mac in safe mode and test to see if this issue continues. Safe mode disables certain software that could be part of the cause. How to use safe mode on your Mac

Also, does the mail appear to be read when you access webmail? If not, the issue may be on the email providers end. 

We hope this helps! 

Sincerely.

Hey there, VinRaiaJr! 

Thank you for posting in Apple Support Communities.

Can you tell us what you mean by reset the read messages? Are messages showing as unread even though you have not read them? Do messages not show read even though they have been read? The more details you can provide the better.

Kindest regards. 

Thanks for the clarification.

Do you have multiple accounts connected to Mail? If so, does this happen on all accounts, or just certain ones? Also, do you see the changes reflected if you look at mail on another device?

We look forward to hearing from you.