[Dovecot] integration of old mails into new dovecot Maildir

I just installed dovecot 2.2.9 on to a new server and want to transfer all the old mails into the email accounts I imported from the previous server into MySQL database. I am not able to view the subfolders and or old mails that I copied into their respective maildir folders. I was very much appreciate if anyone could let me know how to import old mails into the new server. All I see, is the new mails that have come into the account since I started dovecot service in the new server.

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