After switching from Courier IMAP to Dovecot emails are duplicated into POP3 account

PLESK_ERROR: The workaround should be applied during maintenance time with no active connections via POP3. Otherwise, the messages will be downloaded.

1. Create a backup of /var/qmail/mailnames/ directory:

   # mkdir /root/mailnames_backup

   # cp -a /var/qmail/mailnames/* /root/mailnames_backup

2. After switching from Courier to Dovecot, the /usr/lib/plesk-9.0/maildir-migrate-dovecot file will appear.

   # ls -lt /usr/lib/plesk-9.0/maildir-migrate-dovecot
   -rwxr-x--- 1 root root 33861 Mar 26 12:44 /usr/lib/plesk-9.0/maildir-migrate-dovecot

3. Make a copy of this file:

   # cp -p /usr/lib/plesk-9.0/maildir-migrate-dovecot /usr/lib/plesk-9.0/maildir-migrate-dovecot_orig

4. Open /usr/lib/plesk-9.0/maildir-migrate-dovecot file in text editor and edit it in the following way:

   # diff /usr/lib/plesk-9.0/maildir-migrate-dovecot /usr/lib/plesk-9.0/maildir-migrate-dovecot_orig
   174c174
   < if ( $pop3_hdr =~ /^\/[23] (\d+) (\d+)$/ ) {
   ---
   > if ( $pop3_hdr =~ /^\/2 (\d+) (\d+)$/ ) {
   197c197
   < my ( $full_fname, $fsize, $uid, $uidv, $_is_utf8 );
   ---
   > my ( $full_fname, $fsize, $uid, $uidv );
   199,203c199
   < if ( /^([^ ]+) (\d+) (\d+):(\d+):(\d+)$/ ) {
   < # v3
   < ( $full_fname, $fsize, $uid, $uidv, $_is_utf8 ) = ( $1, $2, $3, $4, $5 );
   < }
   < elsif ( /^([^ ]+) (\d+) (\d+):(\d+)$/ ) {
   ---
   > if ( /^([^ ]+) (\d+) (\d+):(\d+)$/ ) {

5.  After this run the command below:

   # /usr/lib/plesk-9.0/maildir-migrate-dovecot --convert --to-dovecot --recursive --overwrite /var/qmail/mailnames