Add an image which is referred to from another part of the email (probably the HTML attachment). You should set the ContentID of the file attachment before passing it in.
[Visual Basic] Public Sub AddRelatedAttachment( _ ByVal fileattachment As FileAttachment _ ) [C#] public void AddRelatedAttachment( FileAttachment fileattachment ); [C++] public: void AddRelatedAttachment( FileAttachment* fileattachment ); [JScript] public function AddRelatedAttachment( FileAttachment fileattachment );