So often I am asked "When did this email go out?" or "Can you verify that they got the enrollment email? They're saying they didn't get anything."
In prior softwares there were "activity notes" that could show the Date/Time that a message was sent. "I can see that we sent the Enrollment email on Thursday at 4:15. Tell them to check their SPAM folder" is a much better response than "Nope, I can't tell. We have to just trust that it sent."
Transparency is key.