Oh, looks like you're right on IMAP. But they still receive mail via SMTP from other servers, there's no way around it if you want to be able to receive email f

Oh, looks like you're right on IMAP. But they still receive mail via SMTP from other servers, there's no way around it if you want to be able to receive email from people not using your service. You need to be confident that their receiving servers encrypt your email without storing an unencrypted copy elsewhere.