Librados Mailbox (librmb) is a library build on top of Ceph's librados to abstract mailboxes.
This library is still in the planning, design and development phase.
The end-goal is to allow for massive e-mail storage on Ceph without the need for CephFS or the RADOS Gateway.
Using native RADOS access and objects e-mail should be stored inside the Ceph system.
Data safety and consistency are guarenteed by using the RADOS semantics and atomic operations.
For easy adoption librmb will be integrated into Dovecot, one of the most popular IMAP/POP3 servers.
It will allow for building massively scalable e-mail platforms using software admins are familair with.
A roadmap is not available yet. As soon as more information is available it will be placed here.
Most of the things which need to happen are described in issue #12430 on the Ceph tracker.