When "Use SMTP Server to Send Emails" is turned on we receive the following error when we use one the following features:
Send Notification Emails to My Inbox
Send Confirmation Email to User
Allow Clients to Save and Resume Later
Email Entry on Entries screen
domain.com says
Error! Unable to send entry.
Error message:
If this feature is turned off and we use one of the above features there is no error, but no emails are sent.