trigger UpdateLeadStatus on Lead (after update) {
    Map <Id, String> leadsOwner = new Map <Id, String> ();
	OrgWideEmailAddress owa : [select id, Address, DisplayName from OrgWideEmailAddress limit 1];
	
    // Go through every lead in the trigger
    for (Lead lead : trigger.new)
    {
        // Check if the status has been changed
        if (lead.Status != trigger.oldMap.get(lead.Id).Status)
        {
            // get the owner ID's that have been affected
            leadsOwner.put(lead.ownerId, null);
        }
    }

    // Map the owner ID to it's email address
    for (User owner : [SELECT Id, Email FROM User WHERE Id = :leadsOwner.keySet()])
    {
        leadsOwner.put(owner.Id, owner.Email);
    }

    List <Messaging.SingleEMailMessage> emails = new List <Messaging.SingleEMailMessage> ();

    // Go again through every lead in the trigger
    for (Lead lead : trigger.new)
    {  
        // Only work with leads that have owners mapped to their email addresses (only those ones have their status changed)
        if (leadsOwner.get(lead.OwnerId) != null)
        {
            // Create an email message and add it to the list
            Messaging.SingleEmailMessage mail = new Messaging.SingleEmailMessage();
            List <String> toAddresses = new List <String> {leadsOwner.get(lead.OwnerId)};
			// set it in meassage as
			mail.setOrgWideEmailAddressId(owa.id);
            mail.setToAddresses(toAddresses);
            mail.setSubject('Automated Email : Lead Status Updated');
            String body = 'The status has been changed on the lead record with ID ' + lead.Id;
            mail.setPlainTextBody(body);
            emails.add(mail);
        }
    }
    Messaging.sendEmail(emails);
}