iPad 7

This might suggest that your SMTP (send) mail server settings and/or account credentials are incorrect. Try deleting and re-adding your email account to your iPad.

Settings > Mail > Accounts > [Your email account] > Delete Account

After deleting the account, perform a forced restart of your iPad:

• On an iPad with a Home button: Press and hold the top button and the Home button at the same time. When the Apple logo appears, release both buttons.
• On other iPad models: Press and quickly release the volume up button, press and quickly release the volume down button, then press and hold the top button. When the Apple logo appears, release the button.

After restarting, you can re-add your email account:

Add an email account to your iPhone, iPad, or iPod touch - Apple Support

Have you removed and re-added the email account as previously recommended?