[old and tired]

Her emails are on a Microsoft Exchange server system,

Where's the Exchange server?

[Boogieman]

I don’t know, probably in an IRS office somewhere. There are offsite backups as well, those need to be subpoenad:

http://hotair.com/archives/2014/06/23/irs-canceled-e-mail-back-up-service-weeks-after-lerner-hard-drive-crash/