I’m in the industry and let me spell it out for you. Server space is limited and most companies have a mailbox size limit. Once you hit that limit, you archive your mail to a local pst file. Then old mail is deleted. That pst file is stored on your local hard drive. There are tape backups of the mail store on the server but those get recycled every so often depend on how you have things set up. Typically backups get stored with a company like iron mountain and they go back 7 years.
The IRS is likely using old junk because, like just about everyone else, they fail to spend properly on technology while handing out inflated bonuses to those at the top. Gov is corrupt and their magic money pot is almost always spent on the wrong thing.
If the IRS was running out of room on their mail store and using too small of mailbox limits, something is wrong and should be fixed. They are not following data retention laws and not investing properly to maintain compliance. They should suffer just as a private business would if not worse.
Then those responsible need to be arrested and brought before a grand jury. Looks like a gotcha.
That used to be fairly common practice. The problem with it is that in an organization of any substantial size having that email scattered out through the network on local .pst files makes legal discovery a nightmare.
The only people who would use this method are organizations that don't ever expect to have their email subpoenaed, and those that do but don't have any intention of complying.
I concur with you. My firm, 500 strong, has a policy about mailbox limit size. It seems that twice a month the IT dept would let me know that I must do the PST file thing to remove the emails from the server. Until I did this, my incoming email box was blocked. As for the rest of your post, I cannot speculate, however, it seems plausible.