We have written an integration piece which places proof delivery (FCP="1") from a CMS to Adobe Campaign and it works fine with externalSource with single email address using the approach mentioned in Business oriented APIs
Essentially, I would like to send proof to multiple email addresses, but from another application (using xtk:persist#Write soap call) and it works fine with <externalSource> approach detailed in my previous comment, but not quite sure how to achieve sending it to multiple addresses using the above approach. Alternatively, would like to know whether it is possible to send multiple email addresses with <externalSource> element?
Let me know you would like to have a look at the delivery xml that we are trying to post via xtk:persist#Write approach. Thanks!