[SM-USERS] can't delete emails from inbox

[JANE C. <jc...@sh...>]

Hi,  I am working on upgrading our current squirrelmail server. 
Centos 5.2
sendmail 8.13.8
dovecot 1.1.17 (imap)
squirrelmail 1.4.17

Seems like I got everything working, I can send and receive emails.  However, when I delete an email in my Inbox, it makes a copy of the email to Trash, but still retain a copy in the INBOX, the deleted email in the Inbox then looks like it has been read, there is an "X".  Then I can purge the email in the Trash.  The deleted email is still there, I can even click on it and read the deleted email.  But in my sent folder, whenever I send an email, I can delete emails in my sent folder.  I do not know if this is a squirrelmail issue or a dovecot issue.  Please advice.  Thanks you. - Jane