Could not instantiate mail function.

I thought I had submitted this but cannot find my earlier ticket.
When I create and event and give it a unique email address notification I get the message: could not instantiate mail function - although the registration is actually complete and goes through. When I remove this unique email notification address for this event the error message goes away. Is this an issue with the component or my hosting service - Siteground ?

PS. I added another email in configuration with a comma and again I got the message: could not instantiate mail function. The registration was completed and went through. Not sure if the registration has gone to the other email address.