When the IRS Says “Lois Lerner’s hard drive crashed” and they lost the emails – that statement is a total lie.
Most business and government systems have email messages stored in many places (see attached diagram) and all of those endpoints are backed up every night and eventually shipped offsite.
So either their entire infrastructure, all their systems, and all their backups were destroyed, or they are lying.
NORMALLY A COPY OF EVERY EMAIL MESSAGE IS USUALLY STORED ON (B), (E), (I), (K), (G), (H), and (J) depending on destination.
Various laws dictate 7 – 20 years of data (internal records) retention requirements.