log how much time to get a smtp connection

app/email_utils.py

@@ -1297,6 +1297,7 @@ def sl_sendmail(
         return
 
     try:
+        start = time.time()
         if POSTFIX_SUBMISSION_TLS:
             smtp_port = 587
         else:
@@ -1306,6 +1307,8 @@ def sl_sendmail(
             if POSTFIX_SUBMISSION_TLS:
                 smtp.starttls()
 
+            LOG.d("getting a smtp connection takes seconds %s", time.time() - start)
+
             # smtp.send_message has UnicodeEncodeError
             # encode message raw directly instead
             LOG.d(