I’m familiar with a multibillion dollar international corporation that uses an excel spreadsheet to communicate between divisions.
Not email or slack or teams or the telephone. An excel spreadsheet.
The left column is where one division enters a message, and the right column is where the other division responds. For a new message, you start a new row. The file lives on a network drive.
I used to see this a lot when a team had to engage with an external vendor temporarily (or not so temporarily), but the only approved software both companies shared was Office before Teams was ubiquitous.
In the worst case, the file wasn't able to be shared live (e.g., SharePoint), so it was just going back and forth in email attachments. That was just as much of a nightmare as you'd guess.
So they were sending emails with a file attachment containing... messages? =_= How about using the emails themselves to, you know... type the message?
The only thing I can muster in their defense is that Outlook search is garbage, and filtering in Excel to find relevant messages may have been marginally easier. But that's playing devil's advocate and going out on a limb.
It was probably in response to some manager saying it's not a good idea to keep documented agreements in email, so some genius thought putting those in an Excel and attaching to email was compliant with that idea.