Associating Emails With Sales Order Records

Hi,

I'm trying to have a fulfillment email sent out via nlapiSendEmail attach itself to the communications subtab of a sales order but am having no luck. I can attach it to the fulfillment and a PO (not that I want to) as follows ("record" is the fulfillment in question):

        var associates = {};            var entityID = record.getFieldValue( 'entity' );          if( isDefined( entityID ) ) {              associates[ 'entity' ] = entityID;          }            var transactionID = record.getId();          if( isDefined( transactionID ) ) {              associates[ 'transaction' ] = transactionID;          }

But when I try for the sales order record neither of the below:

        var salesOrderID = record.getFieldValue( 'createdfrom' );          if( isDefined( salesOrderID ) ) {              associates[ 'record' ] = salesOrderID;          }

or

        var salesOrderID = record.getFieldValue( 'createdfrom' );          if( isDefined( salesOrderID ) ) {              associates[ 'salesorder' ] = salesOrderID;          }