Hi,
I am currently in the process of planning a new deployment of Dovecot. I was planning to use mdbox or sdbox with “mail_attachment_fs = sis posix”, but I stumbled across the following notice in the documentation for Dovecot 3.0 (https://doc.dovecot.org/3.0/settings/core/#core_setting-mail_attachment_fs):
Changed in version 2.4.0 (CE): SIS is deprecated and writing of SIS files is disabled. Reading is supported for now, any missing SIS attachments are replaced with files filled with spaces.
Changed in version 3.0.0 (Pro): SIS is deprecated and writing of SIS files is disabled. Reading is supported for now, any missing SIS attachments are replaced with files filled with spaces.
And https://doc.dovecot.org/3.0/installation_guide/upgrading/from-2.3-to-3.0/ says:
Saving new mails’ attachments via fs-sis is disabled, but reading SIS attachments is still supported. Missing SIS attachments are replaced with files filled with spaces.
What is not entirely clear from this comment is whether this only applied to “sis posix” or also to “sis-queue posix”. Does anybody whether sis-queue is also affected by this?
I saw that the notice was added to the dovecot/documentation Git repository in April 2023, but I couldn’t find any further information there or the main branch of the dovecot/core repository. Maybe, the code for 2.4 / 3.0 has not made it into that branch or repository yet.
SIS sounds like a neat concept and I would like to use it, but obviously I do not want to use a soon-to-be-deprecated feature in a completely new deployment. So, does anybody know an alternative solution for attachment deduplication (except file-system level deduplication)?
Thanks, Sebastian