If you are having trouble sending mail with your iPhone and/or getting an error like "recipient was rejected by the server" check the following settings in your iPhone Settings > Mail, Contacts, Calendars > (the account you are sending mail from).
Outgoing server: mail.smallgod.net
Use SSL
Make sure you are using your full email address for the username and your password for outgoing (SMTP) server authentication.If you are still having trouble try deleting and recreating the account.