On 03 Jun 2015, at 18:29, Juan Carlos Sanchez <juancarlos.sanchez@upm.es> wrote:

Hello:

In case it is defined to use zlib compression, does SIS save attachments compressed?

I have found this question replied in the past (2012) and the answer was NO. I ask again just to know if there have been changes or if it is in the roadmap to add compression.

I have been testing to migrate from maildir+zlib to mdbox+zlib+sis and the results, in terms of space used, and worst than using just mdbox+zlib (without SIS), and suppose the reason in the lack of compression in attachments.

Pretty late reply, but nowadays there's fs-compress plugin. So something like this should work (untested):

mail_attachment_fs = sis compress:gz:6:posix

It's a bit dangerous to enable this for existing attachments though, because if there are any gziped attachments Dovecot will try to gunzip them before sending to client, which causes problems. (So they should be double-gziped to avoid this problem.)