553 you are not authorized to send mail as

It looks like you're trying to send an email, but you're getting an error message that says "553 You are not authorized to send mail as [username]".

This error typically occurs when the email server is configured to only allow emails to be sent from specific email addresses or domains, and the email address you're trying to send from is not authorized.

Here are a few possible solutions:

1. Check your email settings: Make sure you're using the correct email address and password. Also, check your email settings to see if there are any restrictions on sending emails.
2. Use a different email address: Try sending the email from a different email address that is authorized to send emails.
3. Contact your email provider: If you're using a shared email account or a business email account, contact your email provider to see if there are any restrictions on sending emails.
4. Check your email client settings: If you're using an email client like Outlook or Thunderbird, check your settings to see if there are any restrictions on sending emails.