One of the factors that influence the success of COTS product procurement processes is a deep knowledge of the COTS market. The existence of exhaustive and structured descriptions of COTS products belonging to concrete COTS domains may be used as a framework in which particular COTS products could be evaluated and compared to user requirements during the procurement process. Because of its specific characteristics, the domain of mail-related COTS products may benefit from these kind of descriptions. This paper presents an ISO/IEC-based quality model for the mail servers COTS domain, which is built by applying a precise methodology. A general overview of this methodology is presented and its application to the domain is detailed. The use of the mail server quality model is illustrated in some procurement contexts.