On Wed, 2011-03-16 at 14:20 -0700, Daniel L. Miller wrote:

How can I determine what message(s) are linked to a given attachment hash?

That's difficult.. There is no index for that. So you'll have to grep it from all users' storage/m.* files. Right next to that metadata entry should be message's GUID. You can then do "doveadm dump" for user's each mailbox index and find the GUID from there.