I took a look at the code generated when one creates a rule using the FM interface.
Here's an excerpt from the code generated for a rule that moves to a specific folder an email that meets the conditions of the rule:
Code:
if mailboxidexists "c5c83b43-921a-4a80-8324-e36b774e6b68" {
set "L3_VITA_RAC_Volunteer_Hours" "Y";
set "skipinbox" "Y";
}
It looks as if what is happening here is that FM is looking to see if a specific folder exists (not by name) and then moves it there. Interestingly, it seems just to set a flag, and not use the "move" command (which for all I know, just sets a flag!).
I don't know what "L3" means, but the "VITA_RAC_Volunteer_Hours" is a path. The folder "RAC_Volunteer Hours" is at Inbox.VITA.RAC_Volunteer Hours.
So, it may well be worth the effort to change some of my Sieve rules to FM interface rules. The latter seems more robust.