cant send emails on my iPhone XS why?

Try this

1. On your computer, sign in to your email provider’s website. Make sure that all of your email is there or make sure that your email is saved somewhere other than on your iOS or iPadOS device.
2. On your device, go to Settings > Mail, then tap Accounts.
3. Tap the email account that you want to remove.
4. Tap Delete Account.
5. Add your account again.

If the steps in this article don't help, contact your email service provider for more information.

If you would like additional help here, I strongly suggest reading this Tip.

Writing an effective Apple Support Commun… - Apple Community

Read and follow the article linked above.