I'm having a little bit of trouble getting imapsync to behave.

Background: Migrating from Groupwise version 8 to Zimbra 6.0.5 running Ubuntu 8.04 server edition. I'm using Imapsync version 1.286.

Problem: We don't keep plaintext copies of our users' passwords anywhere, so I have to do this migration authenticated as an admin authorised to work on the user's behalf. Here's my script I'm using:

Code:
    --syncinternaldates --subscribed --host1 groupwise.server --user1 user@groupwise --authuser1 admin@groupwise --password1 admin.password --authmech1 PLAIN --sep1 / --nosyncacls --prefix1 "" --skipheader '^Content-Type' \
    --host2 zimbra.server --user2 user@zimbra --authuser2 admin@zimbra --password2 admin.password --authmech2 PLAIN --ssl2
When I run the script as is, it looks like it works fine. When I logged in to check it out, I realised what happened is it took the mail out of ADMIN@groupwise to put into USER@zimbra. Does anybody have any idea what I need to do to make it sync USER@groupwise to USER@zimbra, while still allowing me to authenticate only with the admin password that I have access to?