Add an optional message
Most online services have some sort of invite-a-friend functionality that triggers a pre-populated email. Read through that message one more time. It is probably loaded with marketing jargon (“added value”), and uses superlatives to show how excited the user is (“super excited to finally have everything in one place”).
But is that really the words the user would use?
As an exercise imagine what a good friend of you would write to another good friend of you in her own words to talk about your product.
It might inspire you to write a better pre-populated email message
It might give you some honest product feedback without actually asking these users