autocreate

Warning: autocreate plugin is deprecated, use mailbox { auto } setting instead

auto

Dovecot-2.2

namespace {
    type = private
    separator = /
    prefix =
    #location defaults to mail_location.
    inbox = yes

    ##################################
    mailbox Sent {
        auto = subscribe
        special_use = \Sent
    }
    mailbox Drafts {
        auto = subscribe
        special_use = \Drafts
    }
    mailbox Trash {
        auto = subscribe
        special_use = \Trash
    }
    mailbox Junk {
        auto = subscribe
        special_use = \Junk
    }
    ##################################
}

auto:

• no: Neither
• create: Autocreate, but don't autosubscribe
• subscribe: Autocreate and autosubscribe

* The autosubscribed mailboxes aren't written to subscriptions file

   (unless SUBSCRIBE command is explicitly used for them.)

* The autocreated mailboxes are created lazily to disk only when accessed for the first time.

special_use:

Outlook "Sent" folder

As Outlook 2013 and Outlook 2016ask the mail server for the correct folders first,

making sure that they have been set correctly on the mail server might solve your issue already.

Dovecot

Since v2.1 one can assign SPECIAL-USE RFC-6154 tags and specify,

which mailboxes to create and/or subscribe to automatically.

* special_use: Space-separated list of SPECIAL-USE flags(RFC 6154) to use for the mailbox.