Fair comment, but all of those concerns are mitigated if you:
1) use your own domain(s)
2) take frequent backups
so, even if the purely mail dies, you have access to historical emails and since you own the domains you can migrate to another provider pretty quickly and again, since you own the domain any accounts that are connected to that email address/domain combo are not impacted.
How many people are actively backing up their email on their own? Backing up email seems much simpler than running your own email server, but it's still going to require some technical know how.
To me, the comment that you can just manage your own backups suggests that the service isn't right for anyone nontechnical or technical people who are too busy to backup a hosted service.
I would strongly recommend against using POP3 for such purposes. It doesn’t contain the entire history, for two reasons:
• POP3 doesn’t have the concept of mailboxes. All you will get is the messages that exist at the time of request, not any folders you’ve put them into or labels applied.
• If you delete a message on the server, it won’t be deleted locally, which means that your backup does not represent the current state of affairs.
Also POP3 is definitely designed for the “download and delete on server” approach, and various tooling may have limits on it because of that. For example, if you get Gmail to fetch from some other server over POP3, it stops working after there are 50,000 messages. This undocumented limit bit me some years back when I used Gmail in this way, and it didn’t even notify me that fetching had stopped working! It was two weeks before I noticed that no new messages had been coming in from that source.
> POP3 by design creates a continuous local "backup" that contains the entire history. IMAP doesn't.
I refute this. IMAP is a synchronisation protocol. Clients can choose to operate fully online (performing every operation on the server), fully offline (downloading everything from the server and operating locally) or a hybrid (e.g. keep only the last 30 days of messages locally). The protocol, and most clients, are fully capable of creating a continuous local backup containing the entire current state of the server. Is this “the entire history”? Depends on your definition. I’d argue it’s more true of IMAP than it is of POP3. But it’s not like a Git repository showing what happened and when. I know of no email protocol that provides that. But you can make it so yourself, e.g. sync IMAP into a maildir that happens to be a Git repository and commit after every sync. That would have the entire history, at the resolution of IMAP fetch.
1) use your own domain(s)
2) take frequent backups
so, even if the purely mail dies, you have access to historical emails and since you own the domains you can migrate to another provider pretty quickly and again, since you own the domain any accounts that are connected to that email address/domain combo are not impacted.