How do I delete email from my Apple Watch?

Greetings, Hoot52.

Welcome to the Apple Support Communities. Managing your Mail is important, so we can understand why you’d want more info. 

To delete your Mail: 

“Delete a message: Tap Trash Message.

If you’re looking at the message list, swipe left on the message, then tap .” Manage mail on Apple Watch 

We hope this helps! Don’t hesitate to reach back out if you have questions. 

All the best. 

Unpair your Apple Watch via the Watch app on your iPhone.

Then Re-pair your Apple Watch,this frees up a surprisingly large amount of storage space.And without any loss of your data.

Or this'

If you don’t have enough space to update your Apple Watch – Apple Support