How to configure email Notification in QM01 - Notification Task? Is it SAP standard functionality or can we get it through enhancement only? 

I would suggest to go for the workflow for the said requirement.  As in standard SAP action box there is an option to send the mail. This e mail will go to the Business workflow inbox of the recipient not on the official e mail.
 
I did by customize e mail from Notification with the help of Abap.   You have the options now, select the one which suits you better.

In my previous project I had the same requirement and I worked on basic customization for workflow and some development required if you need to send it through Lotus Notes (where the functional module should get triggered from workflow to send mail to Lotus Notes):  

See the details below:
 
1.  Go to SPRO and activate the Quality Notification worklfow settings.
2.  Go to Tcode: OCCU and activate the necessary fields (you need to spend some time on R&D for the first two steps, first prepare a scenario based on User's requirements)
3.  Work with the developer and find the Std. SAP functional module for workflow, and give him the requirement that whenever the QN sends the mail to workflow it should get triggered to send the mail to Lotus notes. (For this, the respective user's email ID should be added in their SAP user Profile, Tcode:  SU3)
4.  Once the Z functional module has been setup, work with the Basis team to setup a Batch Job, which would refresh the system and send the emails to Lotus Notes.
 
Master Data:
 
1.  Fill the necessary fields for Reference Objects, Subject, and Execution.  Just leave blank for Coordinator, and instead select Goto -> Partner -> and fill in Function – Select IT Interested Party (the User assigned here will act as Coordinator).  This is because the Std SAP workflow will send the mail to all the users if you just mention the user's name in Coordinator field, so you need to maintain the Partner function to send only to the respective Coordinator.
2.  When you save the notification, it will send the mail in workflow to the respective Coordinator, and in turn the Z functional module get triggered and send the mail to Lotus Notes.
3.  The same principle works for Users assigned in Tasks assigned and Task Change.

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