I guess my info was a bit limited, but here are some details.
1. We're using imap with all clients.
2. The error message was as a popup through Thunderbird, but reportedly from the server.
3. We're using different clients, but not (necessarily) on the same user at the same time. I believe I'm the only one to access my account from various clients.
I thought that perhaps the various clients use different flags for i.e. unread, read, unwanted, deleted etc. and that the server could only "hold/define" a limited number of flags???
Anyone having experinced something like this?
Best regards,
Terje