Actual situation: dovecot 2.2.13 on centos 6.5, previously it was a courier server MTA is exim and it used to drop the emails directly in the filesystem in Maildir format, and it still happens for some of the 80(ish) emails. I then moved to a LMTP delivery via Dovecot to use Dovecot compression. Thunderbird is used, and a imap webmail is also available.
There is no quota, by design, biggest mailbox is 54 GB with ten over 30GB.
By design, one user has all the mailboxes of its dept collegues available in Thunderbird.
Users are defined in a test file with this parameter userdb_mail=maildir:/mailboxes/domains/%d/%n/Maildir
In the Maildir the folders are in this format (they use . as separator) and some users are like this: .INBOX.00 IMPORTANT but other are without .INBOX: .00 IMPORTANT Probably the ones with .INBOX prefix were already present in Courier.
doveconf namespace reports namespace inbox { disabled = no hidden = no ignore_on_failure = no inbox = yes list = yes location = ... (lines removed prefix = separator = subscriptions = yes type = private }
To test dovecot tools since some of the emails are "read-only" (can't receive new emails) I tried to move from a Maildir mailbox to a mdbox (also to have a quicker rsync backup) a issued dovecot backup mdbox:/path/to/mdbox/storage that failed with this error message dsync(username): Error: Mail locations must use the same virtual mailbox hierarchy separator (specify separator for the default namespace)
So I started to dig into the problem, discovering that some settings were not set (see doveconf output), that there are 2 different "separator" and that I may, presumably, keep them different on a per-user bases using LAYOUT=fs. I also noticed the .INBOX being present and not present.
I'm looking for informations on how to proceed to have dovecot backup work without losing the mail on disk and have all the Maildirs share a common standard.
I'd like to use dovecot tools, but an option is to creare a new server, create all the accounts, define the accounts in the user Thunderbirds, and do a "move" between the old and new server .... crossing fingers...