This is an update to a kb article at Plesk KB6312 on How to move the Plesk Mail Directory.
I will use the example folder /var/vmail

1. Edit psa.conf

# nano /etc/psa/psa.conf

Changing “PLESK_MAILNAMES_D” to the desired location…

# Location of qmail maildirs
PLESK_MAILNAMES_D /var/vmail/mailnames

2. Then run the following command which will create the new folder and copy the contents of the qmail directory to the new directory…

# cp -a /var/qmail /var/vmail

3. And change the maildirs in Dovecot…

# nano /etc/dovecot/conf.d/15-maildir.conf

Adding the following…

# Plesk Maildirs layout.
mail_home = /var/vmail/mailnames/%Ld/%Ln
mail_location = maildir:/var/vmail/mailnames/%Ld/%Ln/Maildir

4. Run…

# /opt/psa/admin/bin/mchk --with-spam

This will update the following configuration files

/etc/postfix/main.cf
/etc/postfix/master.cf
/etc/default/spamassassin

with the correct paths to your new Maildir.

5. We need to edit the spamtrain script…

# nano /opt/psa/admin/sbin/spamtrain

You will see line 8…

maildir="/var/qmail/mailnames"

Simply change this to…

maildir="/var/vmail/mailnames"

6. Now create the Spamassasin Home Directory…

# cd /var/vmail/popuser
# mkdir .spamassassin
# chown -R popuser:popuser .spamassassin

And restart Postfix and SpamAssassin..

# service posfix restart && service spamassassin restart