This morning while trying to login SquirrelMail on my server I got the error like this ” Preference file, /var/www/html/squirrelmail/data/bikram.pref, could not be opened”. ...

This is easy way to check mail queues on your qmail mail server. I am using Centos server for E-mail Hosting . To view your message in queue simply type following command on your terminal.  qmailctl ...