Greetings, marsie030.
Welcome to the Apple Support Communities. We can understand why you’d want to resolve the issue with being unable to add your Mail account.
First, please Restart your iPhone. Then, review the following resource to ensure that you are adding your Mail account in the required way: Add an email account to your iPhone, iPad, or iPod touch
If so, test to see if you are able to access webmail or Mail on any other device.
We hope this helps! Thanks for being a part of the community.
Sincerely.