I'm designing a system where some but not all groups of users want to share a single mailbox, i.e the user will not have there own inbox. I think this is possible by setting up a user database that returns the same mail location and possible the same home directory. This sharing would only occur in a single domain.

Example User Database

UserID | home | mail

all@site1.example.com | /mail/home/site1.example.com/all | /mail/mailstorage/site1.example.com/all

user1@site1.example.com | /mail/home/site1.example.com/user1| /mail/mailstorage/ site1.example.com/all

user2@site1.example.com | /mail/home/site1.example.com/user2| /mail/mailstorage/ site1.example.com/all

user1@site2.example.com | /mail/home/site2.example.com/user1| /mail/mailstorage/ site2.example.com/user1

user2@site2.example.com | /mail/home/site2.example.com/user2| /mail/mailstorage/ site2.example.com/user2

In this example all of site1.example.com users share a single mailbox, and site2.example.com users each have there own mailbox. Should the home directory also be shared, I read the comment that they should never be shared but wasn't sure if that still applied when the mailbox is the same path. For groups that are sharing a mailbox there would likely be a relatively low number of users concurrently logged in, say less than 10.

For clustering we are currently limited to NFS mail storage. I was planning on using director setup so that the hashing/sharding is performed on the domain only, so all users for a domain will end up on a single node. At this stage clustering is mainly for high availability not performances.

Lastly I'm concerned about possible issues with locking on the mailbox files and indexes. Will one of the mail formats reduces this risk, we can use any format as all mail will be written by Dovecot. Would giving each user there own index location help? and I assume this would mean that each user would see there own flags like read status?

Does this setup sound ok, are there aspects that should change?

thanks,

Jon