It is possible to track individual messages with Critsend. Whereas Tags are used to categorize groups of emails, the "X-UID" header field will let you set a unique identifier for each message. You won't be able to create reports based on X-UID.


How to set a unique identifier

Each email has one header. It contains data such as "From", "Date", "MessageId", and many other useful pieces of information about your message. You can add a field to the header to identify a message using: "X-UID" as a name and a string as a value (ascii alpha–numerical string under 100 characters).


For instance, adding the following field to your header will identify your message with a MD5 hash:

X-UID: 5b72ca59d090412ea187693efee9b15d


Every email delivery software should have an option to add fields into a message's header. Check the documentation of the tool you are using to find out how to add one. In case of doubt, you can always try asking our community in the forum for help.