asterisk users - Jul 2008 - imap voicemail is being sent to the wrong imap account

I am testing the imap voicemail funtionality.  I compiles asterisk using 
version 1.4.21.2 on rhel5.1.
I have two different customers provisioned on the same asterisk as follows:

taken from voicemail.conf:

imapserver=192.168.196.43
imapflags=notls
authuser=asterisk
authpassword=asterisk

; Voicemail for customer 'NJ_ at cust1'
[cust1]
100 => 1234,Mike Oliveras,,,tz=pacific|imapuser=100 at cust1
200 => 1234,Grand Stream,,,tz=pacific|imapuser=200 at cust1
300 => 9999,Joe Blow,,,tz=pacific|imapuser=300 at cust1
400 => ,sipp,,,tz=pacific|imapuser=400 at cust1
800 => 1234,Michael Oliveras,,,tz=pacific|imapuser=800 at cust1

; Voicemail for customer 'NJ_ at cust2'
[cust2]
100 => 1234,Link Sys,,,tz=pacific|imapuser=100 at cust2
600 => ,Joe Blow,,,tz=pacific|imapuser=600 at cust2
700 => ,Fax Line,,,tz=pacific|imapuser=700 at cust2

I am using dovecot as the imap server.

If extension 200 calls extension 100 (both belong to cust1), then the 
voicemail is left in the mailbox belonging to cust2. Also, vmwi is sent 
to both 100 at cust2 and 100 at cust1.  If user 100 at cust1 checks voicemail, 
the response is that there are no messages waiting.  If 100 at cust2 checks 
voicemail, it is successful and vmwi is removed from both phones.

I can send additional debug if needed, but I just wanted to check first 
if tere is any known reason why this would not work.  I also tried 
removing the authuser and authpassword from voicemail.conf and 
provisioned an imappassword for each user and got exactly the same result.

Is there any reason why I can't use the same mailbox number?  This works 
fine when voicemail is stored locally.

Best Regards,

Mike Oliveras