But since they have no accountability, their incentive is to eliminate anything potentially hostile regardless of the collateral damage from false positives. What are their users going to do? Take their business to another big provider that will probably be doing the same, and in the process lose access to a bunch of online services they like because their accounts on those services are tied to the old address? Move to a small provider, which is being forced out of the network by the giants so can't deliver mail reliably?
We are rapidly heading for a world where email is no longer a reliable communications medium for genuine messages between friends, family, work colleagues, etc. The giants are killing email through death by 1,000 cuts instead of a shotgun to the face but the end result is the same.
The problem is that it's much easier to send email than it is to receive it. This puts the onus of spam filtering on the recipient. I'm sad that HashCash or some other PoW scheme was never adopted as a way to force rate limiting of mailers.