Which type of External Account should be used to connect to the mid-sourcing instance in a hybrid installation?

A Campaign must exclude anyone who has received a different email sent from Adobe.
Which table should a Campaign developer query to find the people that have received the other email?

A Campaign developer must create a new table in Adobe Campaign. None of the fields in the new table have unique values.
What should the Campaign developer do?

A Campaign developer is sending proofs for an email delivery. The Campaign developer must indicate what time the proof was generated in the proof email subject line.
How should the Campaign developer accomplish this task?