[Dovecot] *****SPAM***** The folder 'Inbox' cannot contain items. Namespace problems

[Francisco Reyes]

Several attempts to support both Mac and PCs keep failing.

In my latest attempt I used the following settings:

#courier-imap compatibility/Thunderbird
namespace private {
  separator = .
  prefix = INBOX.
  inbox = yes
}

For MAC OS Mail.app
namespace private {
    separator = /
    prefix = INBOX/
    inbox = no
    hidden= yes
}


This last attempt was based on the suggestion of Timo Sirainen,
on the Mac settings.

The PC settings were the defaults I got from the sample config
and have always worked for PC clients.

The new setup with namespace private worked for Mac clients, 
but got the following error for a number of users in both Outlook and 
thunderbird.

Unable to display the folder. 
The folder 'Inbox' cannot contain items. 
This is most likely a limitation of your IMAP server. 
In order to create a folder that can contain items, 
be sure to append / to its name as you create it.


I see this is an old issue.
http://groups.google.com/group/microsoft.public.outlook/browse_thread/thread 
/5f990142171fb792/62adb6c069946e40?lnk=st&q=%22cannot+contain+items%22+dovec 
ot&rnum=1#62adb6c069946e40

One interesting point we discovered was that if we set an IMAP account
in Outlook the very first time we logged in, it worked. If we closed
the client, all subsequent times the "folder Inbox cannont contain items"
error would come up.

doing a TCPdump showed us that the difference was that the first time
that Outlook connects it issued a "Select" command, but all other times
it did not.

Someone suggested to take out
prefix = INBOX.

Would that help?
I don't want to cause problems for the vast majority of our PC users while 
trying to
fix the Mac clients. 

Even though Mac users are a minority of our users, it is extremely 
problematic for us not to be able to support them because many 
domains may have a handfull of such clients.. so we basically 
will not be able to host a large number of domains in dovecot machines, 
just because of a handfull of Mac clients.

Currently using Dovecot r27, but have been having this same problem since 
r15.