I know that the email template on mass email is related only to user and contact, but my question is: there is a way to do a mass email on a custom object?!

This is my apex class:

public with sharing class MassEmail
{
public List<Applicant_test__c> usr{get;set;} //
public List<String> usr_email{get;set;}
public Map<string,string> Map_usr{get;set;}
public string emailid{get;set;}
public string provaemail;
Contact con = new contact();

public void getprovaemail()
{
Contact con = new contact();
con = [Select Id from Contact where Id = :'a0D?fcf=00Bd0000003kLEZ'];
usr=new List<Applicant_test__c>();
usr_email=new List<String>();
usr.clear();
usr_email.clear();
usr=[select Email__c from Applicant_test__c where Keep_in_touch__c=true];
for(Applicant_test__c u : usr)
{
system.debug('___________Email______________'+u.Email__c);
if(u.Email__c!=null)
usr_email.add(u.Email__c);
}
if(usr_email.size()>0)
sendmail(usr_email);
}
public void sendmail(List<String> str)
{
Messaging.reserveSingleEmailCapacity(4);
Messaging.SingleEmailMessage email = new Messaging.SingleEmailMessage();

EmailTemplate EmailTemp = [SELECT id FROM EmailTemplate WHERE developerName = 'Standard_New_Interview'];
email.setTemplateId(EmailTemp.Id);
email.setSaveAsActivity(true);

//email.setTargetObjectId(Applican_test id);

Messaging.sendEmail(New Messaging.SingleEmailMessage[]{email});

}
}

Thanks in advance