@blobcat that is the bauty of federated decentralization. Everyone can choose who they want to collaborate with. This will be an issue for you both with larger or smaller providers. But the reality is that larger providers will be easier for 'the common person' to use, whatever that is. But email shows that. And them protecting against spam and malicious email sources is a product of them being responsible. If you were to meet their standards I'm sure you'd be whitelisted.
I have an email with my fully own domain on my own email thing and I have no issue emailing anyone. Only limitation is that most email stuff don't work with the norwegian characters ÆÅØ for the adress and such.