Problems setting up SIS (duplicate files with same hash)

Joe Beaubien joe.beaubien at
Sat Sep 5 15:40:01 UTC 2015

Hi everyone,

I am currently trying to setup our next dovecot server (2.2.18) with SIS
enabled, but I have enconutered 1 problem and 1 question:

*1) Same attachment, different filenames*

I have a feeling a misconfigured something (or forgot to do something)
because SIS almost works, but not quite since 3 identical attachment take
3x the space (see end of email for my SIS config).

For 3 the emails I sent with the same attachment, I got 3 seperate files
with the same hash name but a different string following the dash:

-rw------- 1 info info 2.6M Sep  5 11:14
-rw------- 1 info info 2.6M Sep  5 11:16
-rw------- 2 info info 2.6M Sep  5 11:18
drwx------ 2 info info 4.0K Sep  5 11:18 hashes

For the record, the "hashes" subfolder has only 1 hash
(e35083e3280a21c6aaabbae8cb23d54493f514a5) which perfectly matches the
first part of the 3 filenames.

*2) Saving attachments under a generic name or more flexible permissions?*

It seems that dovecot saves the attachment with the username and group of
the user who has received the email.

Is it possible to have dovecot save the attachments as a generic user (like
dovecot or dovenull) so that all my different users can share the same pool
of attachments?

Alternatively, is it possible to have dovecot save the attachment under
more flexible permissions so that they can be shared between users?

This would allow us to save alot of disk space.

*Here is the SIS config I am using:*

mail_attachment_dir = /data/emails/attachments
#mail_attachment_min_size = 128k
#mail_attachment_fs = sis posix
#mail_attachment_hash = %{sha1}

Any help would be very much appreciated.

Thank you,

Joe B

More information about the dovecot mailing list