Hello northerngirl222.
Thank you for using Apple Support Communities. It sounds like you're unable to send emails when using the Mail app on your Mac. Being able to send emails is essential. Allow us to investigate this issue and assist in any way we can. We also notice that you're coming from the following resource below:
If you can’t send or receive email on your Mac - Apple Support
This is a great resource to review for when facing issues with your email. To confirm, did you follow all the steps listed within that specific resource? Including removing and re-adding your email account? We'd like you to use Connection Doctor and see which errors populate for your email. Check out this resource for steps on how to use Connection Doctor:
Use Connection Doctor in Mail on Mac - Apple Support
Do you currently have any email filters enabled? If you're not sure this resource can show you how to check:
Filter emails in Mail on Mac - Apple Support
Try creating a new user on your Mac. Then add your email account to that new user to test if you're able to send emails. This step will help us further isolate if this issue is related to a user profile issue:
Set up users, guests, and groups on Mac - Apple Support
Feel free to keep us updated on your results. Best of luck.