Flow:

Listener Configuration:

Transform Message Configuration:

Invoke Apex Rest Method Configuration:

Apex Class:

@RestResource(urlMapping='/MuleSoft/*')  
global with sharing class MuleSoftHandler {  
	
	@HttpPost  
	global static String callEmail( String msgbody, String subject ) {  
	  
		system.debug( 'Inside the callEmail' );  
	  
		try {  
  
			Messaging.SingleEmailMessage mail = new Messaging.SingleEmailMessage();       
			mail.setTargetObjectId( UserInfo.getUserId() );         
			mail.setSaveAsActivity( false );  
			mail.setSubject( 'Important: ' + subject );            
			mail.setHtmlBody( 'From MuleSoft<br/>' + msgbody );          
			Messaging.sendEmail( new Messaging.SingleEmailMessage[] { mail } );           
			return 'Email Sent successfully';  
			  
		} catch( Exception e ) {  
		  
			return e.getMessage();  
			  
		}  
		  
	}  
	  
} 

Output: