Quoting from Jim Correia's mail on Sun, Aug 24, 2003 at 10:54:29PM -0400:
Note that imap servers do not allow adding custom flags.
Some do.
Then, is there any way of probing if such a capability is supported by
the IMAP server? Is there any keyword in the output of either
CAPABILITY or SELECT?
NOTE: I am not an IMAP protocol expert.
It looks like this information comes back from the SELECT command. I'm
looking at section 6.3.1 of RFC 2060 (hoping it is still relevant
today.)
The server I am currently using fetchmail with does not support custom
permanent flags, so I'm interested in seeing it continue to work with
servers that don't support this (as it appears the spec allows.)
Well, each parallel fetchmail will require one separate flag. If there
are only a limited number of flags available (and if we omit flags
like \Answered and \Flagged which are treated specially by almost all
email readers), then there will be unnecessary conflicts and
confusion. This effort is worth it only if their are servers supports
custom flags. The coding is (probably) going to be the same for both
available and custom flags. However, the safer thing to do would be to
go for UIDs.
For example two of the built-in flags are \Draft and \Deleted.
Oops. Ignore.
--
Sunil Shetye.