First, I love reMail. Gabor breathes email and search. If you own an iPhone and use Gmail or Google Apps, get reMail--you'll thank him.
That said, it's easy to skim this article and nod, "Yeah! Yeah!", but when we're discussing these, laymen may need to know a few of these seem over-simplified.
> "TCP connections are great, but for transferring large amounts of email securely, HTTP is the way to go."
1. http://wiki.answers.com/Q/What_is_the_difference_between_tcp... - HTTP uses a TCP connection. For that matter so does SMTP and IMAP and the proposed REMAP.
2. I generally have at least 5 devices using IMAP (on Google Apps) at once, and interleave my interactions with these devices arbitrarily, yet expect each to show me the exact same state when I look at it. Keeping them all in the apparently same state is the sort of intractable software problem bedeviled with implementation details, and I agree throwing out IMAP and starting over with lessons learned could be easier than, say, the RFC linked below.
3. http://ajaxian.com/archives/json-vs-xml-the-debate - Seems this point is something like GIF vs JPG vs PNG, with a bit of "Markdown vs HTML" thrown in. Meanwhile, both XML and JSON are missing an important concept given labels/folders and conversations: multiple references to single objects.
4. Conversations or threads exist today as In-Reply-To: GUID and References: GUID headers, among others, but see the JSON problem above. We don't realize these headers are there because clients generally ignore these and try to group on Subject instead. Gmail grouping respecting existing headers is much better, but from usability point of view, Gmail's approach makes it challenging to bulk delete individual matching messages across a broad set of conversations. For example, to bulk move or mark all messages on a particular date results in the full conversations being moved or marked. So I like this idea as long as I can still optionally operate on sets of messages without affecting the rest of the conversation.
5. http://googlesystem.blogspot.com/2007/08/organizing-chaos-fo... - It's not yet clear that people prefer tags to folders. After all, monkeys don't expect a banana to be in two boxes at once. I don't want to label anything with keywords. I want semantic search.
6. Excellent point. Changing GUIDs out from under us is just lame. Having had to resort to http://github.com/rgrove/larch recently to move a decade of email onto Google Apps because Thunderbird was putting new IDs on each moved message, I fully agree this problem is evil.
7. Seems we're stuck with MIME until we get rid of every legacy email server in the world, or control what servers our recipients use. Between the new server and new clients, sure. But the server will have to know it to send it. Granted, IMAP is for receiving, and SMTP is for sending, but something in the chain has to know MIME.
8. "Call" an HTTP endpoint that "returns" when messages arrive? Just nomenclature, since IDLE is a "call" that "returns" when state changes. Either way, the socket is held open, so neither of these is "push". Maybe Gabor meant "posts back" instead of "returns"? In any case, under the hood, iPhone push and Microsoft ActiveSync are exploiting out-of-band channel such as SMS to notify the phone it should poll (or in case of ActiveSync, maybe doing a "long pull"). See http://msexchangeteam.com/archive/2004/04/26/120520.aspx versus http://tools.ietf.org/internet-drafts/draft-maes-lemonade-p-...
9. Will the RFC specify a search results algorithm, or will the same search return different results depending on the implementation of mail server the client is connected to? We manipulate a "client" tool to perform the search and access the email, so our natural mental model is of the client at hand, not of the remote server. This lets the brain wrap itself around Gmail's web search versus Apple Mail's search box vs OS X Spotlight vs Gabor's reMail all returning different results. Practially speaking, search at the server does make far more sense from both a data retention and security standpoint. I have 509 MB of index in Gabor's "reMail" app on my iPhone, and would rather not.
Thanks for brainstorming this, and thanks for a kickass iPhone app.