ERROR : Could not complete request.
Query: CREATE "INBOX.Sent"
Reason Given: Permission denied
There are three possible solutions for this. You have to find out which one works for you.
First of all, make sure that the IMAP server fuctions with other clients. Remember that SquirrelMail doesn't create any folders or such, it asks the IMAP server to do it. Check that the permissions correspond to the IMAP server user.
Second, you might have misconfigured SquirrelMail. If you use config/conf.pl set your IMAP server with D. Set pre-defined settings for specific IMAP servers in the main menu. Make sure that the delimiter (2. Server Settings/A. Update IMAP Settings/9. Delimiter) and the folder prefix (3. Folder Defaults/1. Default Folder Prefix) are the right ones for your system. If you edit config/config.php directly, check the [presets list] to find useful settings for your server.
Third, make sure that [Security-enhanced Linux (SELinux)] isn't preventing your IMAP server from creating folders or your web server to access your IMAP server. One suggested solution for the latter (which might not work on all systems) is to run the following command when logged in as root:
/usr/sbin/setsebool -P httpd_can_network_connect=1