Problem "send Email with Attachment"

Hi,
I want send an Email with Attachment but I can't attach "xfa","Document Form" type to my mail.
I have :

Cannot coerce object: com.adobe.idp.taskmanager.form.impl.binarycontent.BinaryContentFormIn stance@49dda9 of type: com.adobe.idp.taskmanager.form.impl.binarycontent.BinaryContentFormIn stance to type: interface java.util.List: ALC-DSC-119-000: com.adobe.idp.dsc.util.InvalidCoercionException: Cannot coerce object: com.adobe.idp.taskmanager.form.impl.binarycontent.BinaryContentFormIn stance@49dda9 of type: com.adobe.idp.taskmanager.form.impl.binarycontent.BinaryContentFormIn stance to type: interface java.util.List
at com.adobe.idp.dsc.util.CoercionUtil.toMap(CoercionUtil.java:1201)
at com.adobe.idp.dsc.util.CoercionUtil.toType(CoercionUtil.java:981)

and more.

Any ideas?
Thanks.