On Tue, Aug 14, 2012 at 7:05 PM, Ciprian Dorin Craciun
<ciprian.craciun@gmail.com> wrote:
>     I proposed -- better said queried if possible or at least wanted
> -- to have an internal interface (SPI) that any mail store would have
> to implement in order to be indexed and used by notmuch. I guess the
> interface would be quite lightweight, and would need just the
> following:
>     * open store;
>     * create a cursor iterating through all the emails, yielding only the keys;
>     * read the envelope (as a byte blob) of a particular key; (used
> only for displaying thread lists, etc.;)
>     * read the body (as a byte blob) of a particular key;
>     * maybe create a cursor iterating over all those emails that have
> changed since a particular timestamp;

Someone wrote a fork of offlineimap to store mail in couchdb [1]. The
same couchdb can be mounted with fuse as a maildir [2] for mutt.
According to the author [3], the fuse interface is read only. Assuming
your proposal was implemented, one could complete this work with an
interface to couchdb for offlineimap and get all the features
previously requested.

[1]: https://github.com/theodoreb/offlineimap
[2]: https://github.com/theodoreb/couchdb-maildir-fuse
[3]: http://theodoreb.net/resume