Can't send mail after upgrading to el capitan pop

The joys of upgrading to a new operating system!

If you're unable to send mail after upgrading to macOS El Capitan (or any other version of macOS), there are a few potential solutions you can try:

  1. Check your email account settings: Make sure your email account settings are correct and up-to-date. Go to Mail > Preferences > Accounts, and verify that your email address, password, and server settings are correct.
  2. Reset your Mail settings: Try resetting your Mail settings to their default values. Go to Mail > Preferences > General, and click on "Reset" next to "Default Email Client".
  3. Check for conflicts with other apps: Sometimes, other apps can interfere with Mail's ability to send emails. Try closing any other apps that might be running in the background, and then try sending an email again.
  4. Check your firewall settings: If you have a firewall enabled on your Mac, it might be blocking Mail from sending emails. Try temporarily disabling your firewall to see if that resolves the issue.
  5. Check for updates: Make sure your Mail app is up-to-date. Go to the App Store, and check for any updates to Mail.
  6. Try sending an email from a different account: If you have multiple email accounts set up on your Mac, try sending an email from a different account to see if the issue is specific to one account or if it's a general Mail issue.
  7. Check your DNS settings: If you're using a custom DNS server, try switching to a public DNS server like Google's or Cloudflare's to see if that resolves the issue.
  8. Try restarting your Mac: Sometimes, a simple restart can resolve issues like this.
  9. Check for malware: Run a virus scan to ensure your Mac is free from malware that might be interfering with Mail's ability to send emails.
  10. Contact your email provider: If none of the above steps resolve the issue, contact your email provider's support team to see if there are any known issues with their servers or if they can help you troubleshoot the problem.

If none of these steps resolve the issue, you can try searching online for specific solutions related to your email provider or Mail app version.