IMAP proxy auth - logs in as admin if user is absent

Question

While syncing accounts from an older server to OCUCS with the imapsync script, I found today that when using IMAP proxy auth (with OUCS 7u2 "vanilla" installation) and specifying a wrong user name (unknown to OCUCS), the IMAP server logs absence of the user, however imapsync goes on to put sync'ed messages into the proxy-admin user's account.
I believe this means that failure to proxy-login as invalid user still succeeds as a proxy-user login. (Or imapsync retries this login, and the problem is there - I'll try to research that possibility too).
If the problem is known to be the Messaging server's one, is there any toggle to disable such logins as the proxy user, and return a failure (i.e. user account absence, password mismatch, whatever)?

Answer 1

Ok, upon revising the imapsync script (and parameters I've needed to set for OCUCS), I see this comment in the docs:
You may authenticate as one user (typically an admin user), but be authorized as someone else, which means you don't need to know every user's personal password.
Specify authuser1 "adminuser" to enable this on host1.  In this case, authmech1 PLAIN will be used by default since it is the only way to go for now.
So don't use authmech1 SOMETHING with authuser1 "adminuser", it will not work. Same behavior with the --authuser2 option.
When working on Sun/iPlanet/Netscape IMAP servers you must use --proxyauth1 to enable administrative user to masquerade as another user.
Can also be used on destination server with --proxyauth2 Indeed, I had to use "--proxyauth2" to receive mails into a user's mailbox, and according to your description, the server part seemingly works as designed - so no problem on OCUCS side. I wonder if imapsync script can be amended to detect the "proxyauth" failure and abort, but this is also not an OCUCS problem indeed.
Thanks for the quick and helpful description.