Administering an IMAP server over IMAP connection is not covered by the IMAP protocol. We are not sure it would be a good idea to add support for non-trivial proprietary protocol extensions (this doesn't apply to Quota and Sieve commands, of course).
You can use Rebex
Imap object to execute simple custom commands. For example, to set quota for a mailbox, use this code:
imap.SendCommand("SETQUOTA", "mailboxname", "(STORAGE 10000)");
ImapResponse response = imap.ReadResponse();
if (response.Code != ImapResponseCode.Ok)
throw new ImapException(response);
imap is an instance of Imap class)
Check out How to get quota of IMAP account question for additional information about quota commands.
It looks like there is an IETF draft document) for Sieve on IMAP and we might look into this for one of the future releases. Thanks for the tip!