Oops they forgot.
Check it out:

As the IRS continues to claim it ‘lost’ or ‘threw away’ Lois Lerner’s emails, the agency fails to mention that until recently, they had a contract with an email backup company:

The IRS had a contract with email backup service vendor Sonasoft starting in 2005, according to FedSpending.org, which lists the contract as being for “automatic data processing services.” Sonasoft’s motto is “email archiving done right,” and the company lists the IRS as a customer.

For proof, Twitchy posted this tweet from 2009, in which Sonasoft promoted their relationship with the IRS: