On 24/05/2014 4:27 AM, cpforum wrote:
Yes if you choose dovecot as an IMAP server it's better to use dovecot local
delivery agent.
Related conf in M4 cf file
FEATURE(`local_procmail',
`/usr/local/libexec/dovecot/dovecot-lda',`/usr/local/libexec/dovecot/dovecot-lda
-d $u')
Or Dovecot's LMTP service, which is more efficient than LDA
http://wiki2.dovecot.org/LMTP
FEATURE(`local_lmtp', `[IPC]', `FILE /var/run/dovecot/lmtp')
MODIFY_MAILER_FLAGS(`LOCAL', `-P')
Something I like about using Solaris or Solaris-based OS as mail server
is that you can save a lot of space by just turning on ZFS compression,
since email messages compress well, especially with ZFS gzip compression.
It's probably a good idea for mail with big files attached, but I have a doubt
for small messages (file smaller than
minimal allocation block size (UFS default was 8K/1K. ZFS blocksize is probably
the same order).
I use Dovecot with "mdbox" mailbox format which stores several messages
in a single file, with multiple files per mailbox.
http://wiki2.dovecot.org/MailboxFormat/dbox
This prevents having thousands of tiny files (Maildir) or single huge
files (mbox)
The mdbox files compress well (ZFS gzip compress ratio 3.2x in our mail
spool)
Deduplication would be a better solution when big messages are sent to several
users. To be effective it needs to store big
attachements as separate files so that ZFS recognize duplicate. Then we need to
have and improved Maildir storage scheme
able to split a mail with attachements in several files instead one.
Another powerful feature of Dovecot's mdbox is automatic deduplication
of attachments, a.k.a single-instance-storage. When enabled, Dovecot
saves the attachments on separate storage and uses the MD5 sum of the
attachments to determine if it is a duplicate, even if it is on
different folders (e.g. Inbox + Sent) or multiple users. No need for ZFS
deduplication.
The attachment storage does not compress as well as the mailbox storage
(attachment storage ZFS compression on our server: 1.2x) but this
storage can be sent to separate disks or to NFS servers.
Another feature of mdbox is that old emails can also be moved to
alternate storage transparently to the user. If you are running out of
space in the mail spool, move everyone's old emails to another storage
instead of nagging users to clean up. Or run a cron script to move
emails older than X months to the alternate storage. The users will not
notice any difference.
We use fast drives for the main mail spool, and cheaper larger drives
and NFS servers for old-mail and attachment storage.
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