Sitecore ExM in Depth: How Sitecore Email Experience Manager Determine If Message Was Opened

When you look at source of html email message that was delivered by Sitecore Email Experience Manager you see strange image tag that is located before closing BODY and HTML tags:

<img height="1" width="1" border="0" style="border-color: transparent;" src="http://your.host/sitecore/RegisterEmailOpened.aspx?ec_contact_id=3D0A4C096C4287C4C50A33E8BB5DB87E04&ec_message_id=3D16BE08364227=4836B57FB8CDCEB15C85" />

It is service ExM tag that is inserted to all email. This image tag has source property link to service ExM page: RegisterEmailOpened.aspx. And as parameters are transferred IDs of contact and email. When your mail agent(or browser) tries to load this image it sends request to Sitecore server and triggers event about email opening. Of course it will not work for all mail clients and web mail portals, but it is still good way to get more information about behavior of email recipients. (One of reasons could be not downloading images by default. It is frequent setting for mobile mail agents.)

Sitecore ExM in Depth: Hard and Soft Bounce Detection Facts

There are few facts about soft and hard bounce detection that are not obvious and need your attention,when you try to get messages appeared in "Hard Bounce" or "Soft Bounce" engagement analytics states:

• ExM version is up to 3.2.1 bounce detection works only when messages delivery is performed via Sitecore AppCenter. Setting UseLocalMTA determine if Sitecore MTA(mail transfer agent) should be used. When setting UseLocalMTA is equal true and your  then you will not be able to get hard and soft bounce messages states.
• Starting from Sitecore Email Experience Manager 3.3 you are able to detect bounces with your local MTA. 
• Bounce detection is performed by scheduled task: /sitecore/system/Modules/E-mail Campaign Manager/Instance Tasks/Content Management Primary/Check Bounced Messages. Default interval between running of task is 12 hours 30 minutes. Be patient: contacts will not appear immediately in  hard and soft bounce states.
• Easiest way to check if latest bounce detection was success is to check Items field of Check Bounced Messages scheduled task. It should contain time stamp of latest success bounce detection. If  latest bounce detection was failed this field will contain "1/1/0001 12:00:00 AM" or empty string.
• Bounce detection is performed via request to Sitecore App Center service.