I am trying to create a custom button on List View (Lightning) for sending emails to over 400 people ... All emails will contain personalized info so doing a cc and bulkifying email recepients isn't an option.

I have a custom button on a list view ( which is made up of a VF page) and has ability to select upto 400 records.
The controller for that page is working on a for-loop , but I still ended up with sendMail limit error (cannot execute more than 10 sendMail)

public class ExpertEmailController {
	
   public sObject[] mAct; 
   ApexPages.StandardSetController selectedRec;
   String redirectUrl = System.Label.Redirect_Url;
    
   public ExpertEmailController(ApexPages.StandardSetController controller){
       controller.setPageSize(400);
       selectedRec = controller;
   }
   
    public PageReference sendMail(){
 
        // Send Email
        for ( Monthly_Activity__c ma : (Monthly_Activity__c[])selectedRec.getSelected() ){
        mAct = [SELECT Email
                FROM sObject
                WHERE Id =: ma.Id 
                LIMIT 1];
		            
        // Create body
            string body = 'Dear '+ mAct[0].User +', '+'\n\n';
            body += 'BODY'+'\n\n';

	    Messaging.SingleEmailMessage mail = new Messaging.SingleEmailMessage();
            mail.setToAddresses(new String[] {mAct[0].Email});
            mail.setSenderDisplayName('Salesforce Administrator');
            mail.setSubject('Record');
            mail.setPlainTextBody(body);
            Messaging.sendEmail(new List<Messaging.SingleEmailMessage>{mail});   
        }  
		
        PageReference page = new PageReference(redirectUrl);
        page.setRedirect(true);
        return page;
    }
}

Not exactly sure how an I circumvent this limit.
Creating an out-of-the-box (WF based) email alert on a value update isn't also an option since the records will be locked.

If anyone has any idea, let me know.
Thanks in advance.