Any ideas/plans for how you will do the migration?
Other than that, there's the thing that I need to trust my VM provider, but that much easier than trusting a data mining conglomerate with your private conversations.
In the end, self hosting an email server isn't that big of a deal to set up and maintain.
I've even seen Gmail mark its own address confirmation mails as spam, along with many mails from people I frequently converse with.