Hi Amyams,
We understand you're having trouble with your email server connection. We're happy to help today.
Before getting into further steps, we'd recommend restarting your device if you haven't already done so. Restart your iPhone
If you're still having issues downloading or deleting messages, you'll want to remove and read the account to the Mail app. If this is regarding an iCloud email account you'll want to go to Settings > [your name] at the top > iCloud, then turn off the Mail option. Wait a few seconds and turn it back on.
If this is for a third party email account you'll want to go to Settings > Passwords & Accounts, select the email account then choose Delete Account. Once it's removed just select the Add Account option on the Passwords & Accounts page and follow the steps to add it back.
Add an email account to your iPhone, iPad, or iPod touch
We hope this helps. Take care!