I had a problem in mail queue after upgrading my plesk. Problem was that I had more than 10000 email sent from my IP but it wasn't from my clients. So I tried to solve it. In the parallels forum I get this solution to rebuild my mail settings:
/usr/local/psa/admin/sbin/mchk --with-spam
so I tried it and this is result:
# /usr/local/psa/admin/sbin/mchk --with-spam
==> Checking for: mail_spam_restore... ok
==> Checking for: mailsrv_conf_init... ok
==> Checking for: mail_mailbox_restore... ok
==> Checking for: mailsrv_entities_dump... ok
==> Checking for: mail_admin_aliases... fail
==> Checking for: mail_auth_dump... ok
==> Checking for: mailman_lists_dump... ok
==> Checking for: mail_responder_restore... ok
==> Checking for: mail_drweb_restore... ok
==> Checking for: mail_kav_restore... ok
==> Checking for: mail_spf_restore... ok
==> Checking for: mail_dk_restore... fail
==> Checking for: mail_grey_restore... ok
awk: cmd. line:50: (END OF FILE)
awk: cmd. line:50: invalid char 'ÿ' in expression
unable to process "pop3d"
awk: cmd. line:50: (END OF FILE)
awk: cmd. line:50: invalid char 'ÿ' in expression
unable to process "pop3d-ssl"
awk: cmd. line:50: (END OF FILE)
awk: cmd. line:50: invalid char 'ÿ' in expression
unable to process "imapd"
awk: cmd. line:50: (END OF FILE)
awk: cmd. line:50: invalid char 'ÿ' in expression
unable to process "imapd-ssl"
Errors occured in mail restore procedure
Some utilities was exited with errors:
/usr/lib/plesk-9.0/mail_admin_aliases
/usr/lib/plesk-9.0/mail_dk_restore
after this, in the Plesk services management page, SMTP Server(Qmail) show stop and doesn't start anyway.

I tried to switch to postfix and come back with KB article(http://kb.parallels.com/en/5801), but for switching with autoinstaller I get this error, too:
Downloading the file PSA_9.3.0/dist-rpm-CentOS-4.2-i386/opt/maildrivers/courier-imap-3.0.8-cos4.build93091230.07.i586.rpm: skipped because of md5 checksum match.
Downloading the file PSA_9.3.0/dist-rpm-CentOS-4.2-i386/opt/maildrivers/psa-mail-qc-driver-1.0.0-cos4.build93091230.07.i586.rpm: skipped because of md5 checksum match.
Downloading the file PSA_9.3.0/dist-rpm-CentOS-4.2-i386/opt/maildrivers/psa-qmail-1.03-cos4.build93091230.07.i586.rpm: skipped because of md5 checksum match.
Downloading the file PSA_9.3.0/dist-rpm-CentOS-4.2-i386/opt/mail/psa-qmail-rblsmtpd-0.70-cos4.build93091230.07.i586.rpm: skipped because of md5 checksum match.
Starting installation of packages
Installing the package courier-imap-3.0.8-cos4.build93091230.07.i586
package courier-imap-3.0.8-cos4.build93091230.07 is already installed
ERROR: Unable to install the requested packages because either there is
not enough free disk space left, or there are package dependency problems.
Warning! Not all packages were installed.
Please check if your system services are operable.
Please, contact product technical support.
What can be the problem? space is enough. in the wizard :
Product(s) and operating system packages will be downloaded and saved to the
directory '/root/parallels'.
Required disk space: 1.39 Mb.
Available disk space: 4070.30 Mb.
so disk space is not my problem!
SMTP(Qmail) is stop, yet! Please give me a step by step solution to solve it, ASAP.

Best Regards,
Hamed