[Dovecot] Problem listing SPECIAL-USE flags

[Timo Sirainen]

On 21.12.2011, at 8.24, Michael M Slusarz wrote:

> That's just the reality of IMAP.  LSUB is only useful for grabbing the list of subscribed mailboxes (I *really* hope TB is not using flags from the LSUB response for any meaningful purpose - that is simply badly broken behavior).

It does:

  #   tb-lsub-flags:
  #     Show \Noselect flags for LSUB replies with LAYOUT=fs (e.g. mbox).
  #     This makes Thunderbird realize they aren't selectable and show them
  #     greyed out, instead of only later giving "not selectable" popup error.

> In conclusion, there are 2 ways of handling special-use flags:
> 
> 1. If the server that supports SPECIAL-USE also supports LIST-EXTENDED (RFC 5258), you are in luck.  You can then use LIST-EXTENDED which can accurately retrieve both the list of subscribed mailboxes and special-use flags in a single command.
> 2. If the server supports SPECIAL-USE but does NOT support LIST-EXTENDED, you MUST make a LIST call.  A LSUB call is not sufficient.  It's inefficient, but that's the only way to be 100% sure the information in the response is accurate.

Agreed. I thought about adding the flags to LSUB, but then thought that other servers probably won't do it either. Note how GMail sends them with XLIST command, but there is no XLSUB command.