Disable Email For Single Account on WHM / Cpanel

If you are setting up MS Exchange for your domain hosted on a WHM / Cpanel server setup and migrating from a POP3 / IMAP account to an Exchange email account, soon you will realize that the emails sent by the local server is not being forwarded to the MS Exchange account but rather on the old POP3 / IMAP account. Similar to the situation of this administrator asking people from the Cpanel forums:

"Relay Access Denied" Error When Sending To Office 365 Email Account - How To Fix Microsoft Online Services E-mail Setup

When setting up your new Microsoft Online Services account to your Outlook, you might run into trouble receiving emails coming in but your outgoing emails are sending correctly. For example, you tried using your gmail account to send an email to your Microsoft Exchange email using the Office 365 platform and you get the error: “550 5.4.1 Relay Access Denied”. For this, you might need to do some configurations on your Office 365 account. This requires you to run your PowerShell command prompt. Here are the instructions based on Chris's Blog: