I’ve been playing with zlib compressed mail archives.  I can’t seem to get it to work.  I followed the instructions here:

https://doc.dovecot.org/configuration_manual/zlib_plugin/

I’m not interested in being able to save, just read-only would be great.

I have some compressed mail archives, for example 2020.gz in my ~/mail/ directory.  I have some uncompressed ones too like 2021.  Both are mbox formatted.  In my imap client, I see both 2020.gz and 2021 as imap folders.  I can access mail in 2021 but not in 2020.gz.  It just says it’s empty.

My local.conf has this in it:

mail_plugins = $mail_plugins zlib

I know for sure this is being read because if I change this to some non-existent plugin, I see an in the log complaining about a non-existent plugin.  I’ve tried also adding in the lines for saving but no difference.

Would love to know if there’s something more I need to do.  Also, should I expect to see a folder named 2020 instead of 2020.gz in my imap clients?  My suspicion is that dovecot is treating these as uncompressed imap folders which it can’t read because they look like garbage.  Is there some doveadm command to get it to re-scan folders that I need to run and then realize this is a folder using zlib?

Michael Grant