[Dovecot] processing Dovecot maildirs with shell scripts

[M. Fioretti]

Hello,

I have a postfix server which uses procmail as its delivery agent to
deliver incoming messages to several maildirs. For several reasons,
not really relevant here, I need to process/refilter/sort again the
content of these mailboxes before delivering the messages to the
_other_ maildirs which Dovecot sees and serves to local or remote imap
users. Basically, I need to write some shell scripts that, from cron
jobs, regularly do this:

foreach file in some_incoming_mailbox/new/
 do
 #process the file and/or set some variable according to its content
 delete the file or
 mv it to some_other_maildir/new/

where the actual action and value of some_other_maildir is set every
time by the "process the file" part of the script.

The part that I still miss is guidelines to do these things safely,
that is without losing or corrupting messages or doing anything else
that would confuse dovecot.

For example, under which conditions it is sure to move or delete (the
Unix way, with mv or rm) a message from mailbox1/new/ to mailbox2/new,
when the latter is served via dovecot to remote users?

What is advisable and most efficient? Use locks (how?), only work on
file which are at least one minute old? Should I move the messages to
tmp instead of new? What else?

Tips or pointers about this are very welcome.

Ciao,
	Marco