Hello Experts,

In my org, there are 3 Public group.PG-A,PG-B,PG-C.

PG-A has 2 Users having RCU Initiator profile.

PG-B and PG-C each has 1 user.

I have a requirment,

When Case passes from PG-A (RCU_Stage__c='RCU Initiator') user to PG-B (RCU_Stage__c='RCU Verification') to PG-C (RCU_Stage__c='RCU Completion'), Once RCU_Stage__c become 'RCU Completion', email should send to the User who passed the case to PG-B user.

Allocated_By__c is the case field which shows the User (Who send the case to 'RCU Verification' (PG-B) stage.

***I dont want to write HardCoded email id in sendTo***

My Code-

trigger sendEmailtoinitiator on Case (after update) {
    
    //master list to hold the emails we'll send
    List<Messaging.SingleEmailMessage> mails = new List<Messaging.SingleEmailMessage>();
    
    for (Case newCase : Trigger.new){
        if(newCase.RCU_Stage__c == 'RCU Completion' ){
            //Create a new Email
            Messaging.SingleEmailMessage mail =  new Messaging.SingleEmailMessage();
            
           //Setting list of people to get the email
            List<String> sendTo = new List<String>();
           // sendTo.add(newCase.Allocated_By_Text__c);
            sendTo.add(newCase.Allocated_By__c);
            mail.setToAddresses(sendTo);
            
            //Setting ReplyTo email 
            mail.setReplyTo(newCase.OwnerId);
            
            //list of people who should be CC
            List<String> ccTo = new List<String>();
            ccTo.add(newCase.CreatedById);
            mail.setCcAddresses(ccTo);
            
            //Email TemplateId (NOT SURE)
            EmailTemplate et = [select id,Subject from EmailTemplate where developername='CaseStageEmailAlert'];
            mail.setTemplateId(et.Id );
            
            //Subject
            //mail.setSubject('Case reached at Completion Stage');
            mail.setSubject(et.Subject);
            
            //adding email to master list
            mails.add(mail);
            
        }
    }
    
            //Send email to master list
            Messaging.sendEmail(mails);
}