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Greetings,
On Fri, 2017-10-13 at 11:34 +1000, David.M.Clark wrote:
Just went through this one recently using CentOS with SendMail, Procmail and IMAP conversion from mbox to Maildir - I needed to make sure I could run both formats while I migrated users one-by-one.
When I have migrated solutions from mbox to maildir (I have done more than one) I found it easier to get a mail client to do the hard work for me (if you're on a LAN with the server it's faster). I created new usernames with maildir as their base, and copied the folder over. This approach could be automated, probably easier than going via a script to open each mbox and push each message through an LDA. There are a heap of examples around for connecting to IMAP via PERL (https://www.example-code.com/perl/imap.asp is good). If you write your perl script properly you could migrate multiple users at once from the cli ... xargs is a wonderful tool :). Unless you are hosting a mail service that needs to be up 24/7 you should be able to migrate large amounts of mail out of hours. If you have users that have been using POP to get their email and want to move them to IMAP it's also easier to have the MUA do the work (I have migrated users from using POP and local storage, to remote IMAP this way - especially users of MS Outlook).
In essence I am using /etc/procmailrc and the users_db approach to get e-mail delivered correctly after I have converted an account to Maildir format. I also never trust anything in my IT life, so I backup the mail directories under $HOME to mail_old.
Yeah, safe bet there. Creating copies before starting the migration process is the best way (depending on the underlying filesystem also probably faster if you need to restore something). Even using a second copy as the base to push things from mbox into a new maildir.
While I like procmail (it has some nice features), I also migrated things to sieve a while back. There are a couple of things I can do with procmail that I have found it hard to match with sieve, but properly nested if statements mean I can traverse my rules faster. Most people will end up using MUA filters on an inbox rather than a procmail/sieve setup (the number of MUA's that support either of these server side filters is minimal, and the number that support them properly is even smaller - I did have a webmail client destroy my nested "if" statements). Using procmail or sieve as an intermediate step for initial transition from mbox to maildir is a safe bet, then it comes down to having dovecot setup properly to deliver into maildir.
Nikolai Lusan nikolai@lusan.id.au -----BEGIN PGP SIGNATURE-----
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