Not sokoloff, but that would be a reason to move to another mail provider. If Twitter is censoring speech then the correct option is to move to another service or host your own speech. People talk about social media monopolizing the discourse but the only barriers here are network effects, and people can move to other forums (I, for example, do not use Twitter or Facebook and still manage to have online discourse). This is different than if it were censorship at the ISP level, where there are physical and legal barriers of entry which make switching a difficult or impossible option.

Separate, but equal?

There’s a distinction between one-to-one messaging and one-to-many messaging that needs to be considered. But in general, Google doesn’t control the email protocol so I don’t see a problem with them refusing to send an email they deem objectionable.

This is why private email services and roll your own exist.