The SocketLabs On-Demand delivery infrastructure allows for senders to tag each outbound message with two custom identifiers [MailingID, MessageID] that help improve reporting capabilites.  These values are included in the message header before SMTP injection, or they are specified as a parameter in the HTTP Injection API.  For more information on setting up these values in your outbound messages see our API reference documentation.

As we continue to design and innovate new features in the SocketLabs On-Demand Control Panel, the proper utilization of these values becomes more and more crucial.  Allowing users to specify these values in the message headers restricts our ability to enforce validation on these fields.  We want to emphasize the best practices in regards to these values to ensure our systems give you the best possible experience.

There are two best practices that are very important to understand when designing a system for utilizing these values:

1.  MailingID should NOT be unique for each and every outbound message. The MessageID was designed as a unique message identifier.  MailingID was designed as an identifier for groups of messages such as campaigns, jobs, or batches of messages. We are really excited about some new Control Panel reporting features in the pipeline which will allow you to gather more insight into your email.  These new features give users the best possible experience when following best practices with these unique identifier values.

2.  Total combined character length of both MailingID and MessageID fields should be less than 30 characters.  Exceeding this limitation can cause deliverability issues with your outbound messages.  For more information about why this happens see our knowledge base article on Variable Encoded Return Path.

Any further questions about using the custom MailingID and MessageID values can be directed to our Support Department.