[exim] Exim with SQL message store

Hello,

exim is our MTA of choice for more then 10 years now, but we are very
unhappy with the message queue. Header, body, delivery attempt logs and
delivery hints are spread throughout dozends of subdirectories, text
files and berkeleydb files, which make it very hard to look at the queue
in depth, like "show subject and queue-in date of all messages by
authenticated_id x and freeze them". The exim tools are a nice start for
easy tasks, but it is almost impossible to work with the queue and query
or operate on it directly since it is mostly text based and only exim is
able to get the structure with its parsing routines.

I have not looked into the queue source in detail, but does exim keep an
abstract layer to access to queue, so it would be possible to replace
the current text file queue to an sql backend? Or does each exim twiddle
directly in the files, adding delivery attempt counts, new headers etc.?

Regards
Marten