Reading https://gdpr-info.eu/issues/personal-data/, it seems you could use the GDPR for, well, unexpected request. For example, if I ask Google to remove any email from me I have send, not only from my account (you can do it yourself easily, BTW) but also from the account of the people who have received the mail (provided it is still there and owned by Google) and the Google server. I do not see why that's would not be possible. At the other hand, at least in some countries (Belgium, for example) email is the legal equivalent of a paper letter and can be used to prove something (that you have agreed to a contract, for example). This would obviously jeopardize this. Note that a paper letter would not be necessarily better... Has someone an experience about how the GDPR is interpreted?