Transition Team's (TTT) emails produced to the Special Counsel without the TTT's knowledge or consent pursuant to a letter:
http://www.powerlineblog.com/archives/2017/12/muellers-little-surprise-4.php
It suggests there was no subpoena or legal process, nor apparently was their consent of the owner of the records (i.e. the TTT), rendering the Special Counsel's statement on the affair a lie.
The letter itself is here:
https://www.ronjohnson.senate.gov/public/_cache/files/5a410139-0c0a-44e0-b8ff-731b1863c53a/2017-12-18-rhj-to-murphy-gsa-re-tfa-material.pdf