Name: imap_inprogress_interval
Type: DURATION
Default-Value: 10s
Last-Modified: 3.12.0

The interval after which the server will send an "INPROGRESS" response code
to the client during a long-running imap command (e.g. search, copy).  The
default is 10 seconds.  The minimum value is 0, which will disable
"INPROGRESS" response codes.
