The error is present when the Outgoing SMTP server email settings (hostname, username, and password) aren’t properly configured on your device.

If you are a SiteGround customer, find your email settings in Site Tools > Email > Accounts > go to the kebab menu Mail Configuration.

Next, access your iPhone and navigate to:

Note: In case you don’t know your email password you can change it from your Site Tools > Email > Accounts > go to the kebab menu Change Password.