The CID property sets or gets the content identifier.
Sets or returns a String value.
A CID should only be set if the content is referenced in a URI of a text/html content type.
Code in the Mail_OnStartRender handler:
Mail.Contents.Add("chart")
Mail.Contents("chart").URL = "http://www.emilltest.com/chartapp/renderpie.asp?v1=12&v2=38&v3=50"
Mail.Contents("chart").CreateCID
Some content:
<body>
See the following pie chart: <img src=<%="CID:" &
Mail.Contents("chart").CID%>>
</body>