We have a receive connector to relay email sent from application. one of owner application informed me that his application failed to send an email.
I'm checked there is no report from other application owner.
Based on protocol log, (attached). the application server tried to make SMTP session with receive connector at 14:00 but SMTP session doesn't completed. On 14:01, the SMTP session able to establish and the application to send an email.
My question why the 1st SMTP session (RED) attempt failed? Where do I checked? Any log or event available.
I notice that the 1st SMTP session (RED), the remote server didn't sent "HELO" command why on 2nd SMTP session (GREEN) the application server did sent "HELO" (Row 9) and receive connector did reply to the "HELO" (Row 10). Is that the issue?