IMAP can also send other instructions like Delete.

You might want to consider POP3.

You can setup most IMAP clients to keep a copy of all messages.

It can't delete an automatic or manual backup I've made of all/some of my email.

I think the argument is that you have a way to export and retain emails while there is nothing you can do with messages on FB other than screenshot.

If the argument is that I can go out of my way to back something up outside of the regular framework of the software, I could do the same by saving messages from Facebook.

Email backups have been standard for decades. There are solution that follow standards and have been tested in audits. Taking screenshots of Facebook messages is very different from that.

You could either save the HTML or pretty easily use some JavaScript to extract the message contents to plain text.

But convincing courts and auditors that this is the original version of that time will be harder with a self-written script than with email backups.

I suppose that's true, but isn't there some precedent for dealing with Web pages? This can't be the first time this has come up.

> There are solution that follow standards and have been tested in audits.

I don't think their point was that you can get text vs images.

Can, but it doesn't mean that they send. My IMAP accounts keep emails on servers, and in my client.

You can but only when you're online. And in general everything can be gamed, including email, given you depend on someone in receiving information.

So FastMail's argument is just logically inconsistent. More, an agency problem is here.

I have copies of my Fastmail mail on several computers and access the mailboxes when online or offline. It syncs perfectly, is backed up through normal backup techniques and I am in control. There is no mystery here.

but wouldn't that just depend on your mail client?

its technically possible to edit the mail body on the server side and serve the modified message under the same mail ID.

I'd wager most clients would invalidate their local copy and trust the new mail from the server, but have to admit that I've never tested such a scenario.

iOS and Apple mail don’t. Some servers sometimes have the issue of reusing message identifiers and both clients would show the wrong content for the mail. You’d have to force a resync of the whole Mailbox to fix this.

Also: A backup of the mailbox would be unaffected by any server-side change.

most imap clients wouldn't even notice. Once that message is downloaded there's no reason to download it again.