I'm using Gnus v5.10.3 (from Debian/unstable) to read mail on an Exchange
5.5 server via IMAP.  It works well in general, but I'm having problems
splitting my incoming mail.

I'm using a simple group mail splitting setup ('to-address' group parameters
defined where appropriate), and if I visit my inbox ('nnimap+lan:INBOX' and
hit 'B q' on a mail that I think should be split into another group, I get
the expected result (example: 'This message would go to zope.user').
However, if I try to respool the message with 'B r', I get errors like:

Copying to nnimap: (1503)...
Protocol Error: "Invalid ASTRING for folder name found in APPEND command"
Couldn't Copy article 1503: Protocol Error: "Invalid ASTRING for folder name found in APPEND command"
nnimap: Updating info for nnimap+lan:INBOX...done

My "test" group was originally named "Mailing lists/Zope", but I thought
that the "/" might be causing the problem, so I created the new "zope.user"
group and moved all of the "Mailing lists/Zope" messages into it.

Any thoughts of where I might look to troubleshoot or fix this?  I'm going
crazy with having all of my mail come into my inbox - how can people without
mail filters stand this?
-- 
Kirk Strauser