Dovecot requires emails in maildirs to have ,S= -flag on emails to be compressed, but I cannot seem to find a way to make Postfix to add this flag. Is there some configuration option or is there other recommended way to get the filenames to have ,S= in them, eg.:

  • Use dovecot's ltmp transport to deliver from postfix to local users. You get the advantage of the s= value being added as well as hardlinks between messages delivered to multiple local users (assuming UID for all users is the same in a virtual mail environment). – wurtel Feb 1 '18 at 9:28
  • How do you make Dovecot add those s= values, I dont seem to find a way to do that, by default they are not added – Raynet Feb 1 '18 at 17:48
  • If you use dovecot's LMTP transport to deliver mail to the user's Maildir then those are added by default. If you use postfix to deliver directly into the Maildir then postfix does not add them. Put something like this in postfix's main.cf: virtual_transport = lmtp:unix:private/dovecot-lmtp – wurtel Feb 2 '18 at 7:44
  • I am using lmtp to deliver mails now, but it is not adding that size value. Added virtual_transport = lmtp:inet:<ip>:<port> to my Postfix main.cf. – Raynet Feb 2 '18 at 7:54

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