Battery Problem from Mail Activity Background

Greetings, SandiMahendra!

Thanks for reaching out to the Apple Support Communities! It sounds like you have deleted the Mail app but the app is still running in the background and using battery. Did you delete the app in the past 24 hours?

I suggest checking out this article for Batteries - Maximizing Performance. This can give you information about apps running in the background:

"Background Activity. This indicates that the battery was used by the app while it was in the background — that is, while you were using another app.

• To improve battery life, you can turn off the feature that allows apps to refresh in the background. Go to Settings > General > Background App Refresh and select Wi-Fi, Wi-Fi & Cellular Data, or Off to turn off Background App Refresh entirely.
• If the Mail app lists Background Activity, you can choose to fetch data manually or increase the fetch interval. Go to Settings > Accounts & Passwords > Fetch New Data."

The article will also give you additional steps you can take for optimizing the battery performance on your device.

Let me know if you continue to have issues and have a super day!