You are expecting an important email from the client, he just confirmed over the phone that the mail has left his outbox but the message is nowhere to be found in your inbox. An hour later, the email finally arrives.
Emails are usually delivered in a second or two so why did it take so long for this particular message to reach your mailbox? Was it due to the attachments? Or was there a problem with your mail server?
You can usually find the reason for the delay in the email message itself. Open the message inside Gmail and choose Show Original to view the message headers.
Here you will see a list of machines (or servers) that a message had to pass through before reaching the recipient’s mailbox. The IP addresses are listed in the reverse order so start from the bottom all the way up to see the actual path travelled by an email message.
The message headers may appear complex and geeky but they really aren’t. For instance, the following line from the headers simply indicates that Google’s mail server received the message from Hotmail servers on 29-Jul-2012 at 07:25:37 (PDT).
Received: from dub0-omc3-s2.dub0.hotmail.com ([18.104.22.168]) by mx.google.com with ESMTP id 92.2012.07.29.07.25.36; Sun, 29 Jul 2012 07:25:37 -0700 (PDT)
Now copy the full message header to the clipboard and paste it into Google Apps’ Toolbox. This tool will analyze the email’s path and, based on the timestamps when it passed the different machines, it will tell you the exact source that is responsible for delaying the message delivery. Here’s a sample report:
The toolbox is part of Google Apps but it should be able to analyze messages from other Outlook and other email programs as well because the message headers have a standard format.
Related: Find the Sender’s Location in Gmail