Transferring email accounts with the emails still in them is usually unnecessary.
Can you not simply download all of the emails from the old server onto your computer, then delete those email accounts and re-create them on your new server?
It's probably more straight forward then trying to transfer the accounts as well as all the emails which are inside them.
well the problem is that my client doesnt live in my country & outlook express is not working on his computer so he is using the webmail (Squirremail) which is featured in Cpanel . I dont know if there is the download emails possibility in it, I will look at it, hopefully there will be something.
Did you get ssh with your old reseller? if you did you can ask your new reseller to copy all the account information over to the new server for you hassle free.