Sophos mail log does not show recipient

Question

My client have issue about Sophos mail log. When display mail log some of recipients are disappear, but e-mail could send normally. What should i solve it? 
 PS. Cisco ironport is working front of sophos (Ironport > Sophos mail protect) 
 Thanks!!

Jaydeep · Answer

Hi Phawin Khachornklinmala 
 These empty log lines indicate unsuccessful communication. If communication fails after the first message in SMTP, the sending server will initiate another connection and it would show up here as blank. You may check the details into logs to see more.