Crucially the market for email providers is really broad, easy to enter, doesn't have explicit lock-in (although it's a potentially huge job to change your email address, this can be made easier by having your own mail domain), and doesn't have one or two big players making the rules.
Most systems including gmail will let you whitelist senders. You can't whitelist apps onto an iPhone without jailbreaking it.
Most systems including gmail will let you whitelist senders. You can't whitelist apps onto an iPhone without jailbreaking it.