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:
- Settings > Mail.
- Go to Account > Outgoing Mail Server and select SMTP.
- Select your Primary Server.
- Fill the Outgoing server Host name, your email address (e.g. firstname.lastname@example.org) as Username and place the email password accordingly.
- Tap Done to save your changes.
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.