I had a family member work at a company that blocked gmail. They were a lotus notes shop tied with MS AD, and their admin was very anti-google. "Gmail is a cesspit of spam" or something like that. But... then was all in on MS. "MS is great - they have no spam problems". Which is just... wrong.

So... I couldn't email my family member at their work from my gmail. Not a big deal for me, but I know it impacted their ability to work with some clients and providers. And then... sure enough, they were getting spam from MS-hosted stuff (outlook.com, azure hosted stuff, etc).

He might have thought he was getting one over on google or something like that - I'm sure they didn't give a toss about it.