In Plesk, its quite simple to configure DNS settings.  This post will guide you on how to setup Google apps on Plesk panel 9.x.x

Lets get started! You must have an active account, meaning a registered domain .

Login to Control Panel https://control.DNN4Less.com/cp

Go to your domain. Click the "DNS Settings"

Before adding any records, delete all mail records first. See the image below.

After deleting click the "Update" button. See the image below.

Click "Add record"

From the below image you need to put all the MX records orderly on your Plesk DNS settings.
First add all the MX records one-by-one see image below:

Slelect Record Type "MX"
Leave "Enter Mail Domain" empty
" Enter Mail Exchanger" for the following Mail Exchangers

Put all the records and follow the MX Priority accordingly.

ASPMX.L.GOOGLE.COM
ALT1.ASPMX.L.GOOGL.COM
ALT2.ASPMX.L.GOOGLE.COM
ASPMX2.GOOGLEMAIL.COM
ASPMX3.GOOGLEMAIL.COM
ASPMX4.GOOGLEMAIL.COM
ASPMX5.GOOGLEMAIL.COM

After adding click the "Update" button. See the image below.

Your DNS records will be look like this.

You are now done on MX records for Plesk now we need to modify some configuration on Plesk to tell Plesk that we dont want to use the built in mail.

On your Plesk dashboard click the Mail Accounts.

Click Mail Settings

Uncheck "Activate mail service on domain"

And save by clicking OK.