fix(email campaign): send emails using bcc

(cherry picked from commit 7e8d19b0c8)

erpnext/crm/doctype/email_campaign/email_campaign.py

@@ -123,7 +123,7 @@ def send_mail(entry, email_campaign):
 		subject=frappe.render_template(email_template.get("subject"), context),
 		content=frappe.render_template(email_template.response_, context),
 		sender=sender,
-		recipients=recipient_list,
+		bcc=recipient_list,
 		communication_medium="Email",
 		sent_or_received="Sent",
 		send_email=True,