An e-mail message is received that specifies at least one recipient and which includes an attachment. The attachment is a file having a header specifying at least one e-mail address for a permitted recipient. The header is analyzed to determine whether the at least one recipient is specified as a permitted recipient. The e-mail message is relayed to the at least one recipient if is determined that the at least one recipient is a permitted recipient. In addition or in the alternative, delivery of the e-mail message to the at least one recipient is prevented if is determined that the at least one recipient is not a permitted recipient. Related apparatus, systems, techniques and articles are also described.