Yes this is possible. We have recently built something very similar. Here is how you could set this up: - Create a standard program and add a my.token - (will be used to parse your html) - Create your email alert and insert that token in the body of your email - Build a smart campaign that will have a request campaign trigger (optional) , your user in the smaratlist filters, and send your email as a flow - Use the API to trigger or shcedule the campaign and attach your HTML content within the token attribute.
You could use the Request campaign or Schedule campaign API calls to execute the email send: http://developers.marketo.com/documentation/rest/request-campaign/ http://developers.marketo.com/documentation/rest/schedule-campaign/
My understanding was that you where doing one HTML for multiple Leads, but from your previous comment is seems like it's one HTML per lead, right?
Do you have a large volume of leads/HTML combinations to deal with? If so, then, the Request Campaign that Murtza Suggested might be your best option. My understanding is that you have only one Token value passed by API Call - so It would require 1 API call per lead.
Another alternative could be tu store the HTML Data within the lead record. Then you can 1) update Lead with HTML using API 2) Request or schedule campaigns in batch. In this case (using lead field) I think you would be limited in the lenght of 3,200 characters and I'm not 100% sure how encoding-decoding could affect the structure.