Your approach could indeed give more traceability as for if the email was sent (although I agree with @Mark to be very careful in storing this in gmail), but that rarely ever is the problem in my experience.
Usually the email was sent but not accepted somewhere in the mail route. If you find that acceptable as it is not your responsibility to actually *deliver* it, then you're done. If you're leaning towards guaranteed delivery, which you should as nobody cares that you sent it if it was not received, then a whole world of inconsistencies open up. Read this and wheep:
That article does not even cover the various exceptions that may be needed per email service provider. This is why the bigger, public websites usually outsource the sending of mass emails using 3rd party services.