Hello,
I found a posting on the mailing list from 2008 "Adding new storage backend to Dovecot" while searching for POP3 and IMAP servers, that allow to use a NoSQL backend rather than a traditional file system.
The problem with traditional filesystems is, that they are very limited. You cannot easily extend it, even with RAID 10 all messages may be lost due to a RAID controller failure and just-in-time backups of a heavy loaded system with consistently changing messages folders are virtually impossible.
Modern object stores like Scality, CouchDB or MongoDB can be very handy, as they easily allow to keep an arbitrary amount of copies of each message on different servers, you can simply add a storage node and new storage is immediately available and mailboxes aren't bound to a certain server any longer, but messages are evenly distributed across all storage nodes, thus distributing load as well.
Since the original posting was dated 2008 I was in good hope, that someone worked on that already, but at least in dovecot-2.0.9/src/lib-storage I couldn't find anything relating to NoSQL message stores.
Isn't this option of big interest for every bigger mailbox provider? How hard would it be to develop? Would it be possible to get this developed on a paid basis by the dovecot core team?
Kind regards Marten