Updated: IRS e-mails not lost after all
On a side note, Tapes are a terrible DR system if you have a lot of data to store (as I am sure the IRS has). Restore times are slow and you would have to rebuild your infrastructure and restore back into to it. It's why almost every big datacenter utilizes replicated SANs and standby Virtual Machines. Given the procedure to recover Exchange Server email via tape, its not surprising it took them months to do it. That said, we utilize an email archiving system and have a standby DR VMs of all our exchange server infrastructure. I could have restored those emails in less than a day on our system (probably just a few minutes).