<xsd:complexType name="mailType"> <xsd:sequence> <xsd:element name="envelope" type="ml:envelopeType"/> <xsd:element name="body" type="ml:bodyType"/> <xsd:element maxOccurs="unbounded" minOccurs="0" name="attachment" type="ml:attachmentType"/> </xsd:sequence> <xsd:attribute name="id" type="xsd:integer" use="required"/> </xsd:complexType>