The answers to the clues below will have something in common.

1. Innovate, challenge previous limits
2. Romantic 1957 Pat Boone song
3. Romantic 1962 Brian Hyland song
4. "It's over" correspondence
5. Oscars phrase
6. How Elvis sent a letter in song
7-10. Girlfriend's response to Elvis' letter

Answers:

1. Push the envelope
2. Love Letters in the Sand
3. Sealed With a Kiss
4. Dear John letter
5. The envelope please
6. Special D
7. Return to sender
8. Address unknown
9. No such number
10. No such zone