[Dovecot] Problem with zlib plugin and flags

[Jeremy Maryott]

Hi,

I'm working on enabling the zlib plugin and compressing most of the mail
on my mail server, and I've run into a bit of a problem with doing
things as described on the wiki's zlib plugin page (here:
http://wiki.dovecot.org/Plugins/Zlib). I'm using Dovecot 1.2.15 and
maildir as a mailbox format on Debian 5.

I have a script that implements the steps listed at the bottom of the
wiki page. The problem has to do with step 5, which recommends that you
add a 'Z' flag to each email that you compress so that you don't
compress it again. The problem that I ran into is that when you move an
email to another mail folder, this flag appears to go away. As a result,
my script has compressed some emails that were already compressed,
rendering them unreadable by Dovecot.

I've mostly solved that problem, and my compression script now runs
'file' and looks to see if it's gzipped already for each file that's a
candidate for compression. I'm not sure this is the best solution (it's
definitely slower than just checking the filename), so I'm open to
better alternatives.

Reading http://wiki.dovecot.org/MailboxFormat/Maildir, I see that
Dovecot supports 'non-standard fields' specified after normal flags and
a comma. It seems like that might be a better place to put the 'Z' flag,
if Dovecot won't retain it when places with the normal flags. I'm unsure
how the filename would look if it doesn't currently have any flags,
though. Would there just be two commas in a row, followed by my
non-standard flag?

If I haven't missed or misconfigured anything and what I said above is
correct, the wiki should be changed so others don't run into the same
problems I have. I'm happy to do so, but I didn't want to make any
changes without making sure I was right about what was going on.

Thanks,
Jeremy