Hey there! The best answer is "probably, but not an automated tool." It really depends on the storage type, but most Postfix implementations that I've seen use mbox. You'd likely need to do something like this:
-create the email account in cPanel
-copy over the password and place that in the /home/$user/etc/domain.tld/shadow and /home/$user/etc/domain.tld/passwd files as appropriate
-copy over the mail data into the cPanel directory structure
I'm sorry I don't have a more automated option available.