/// <summary>
        /// Initializes a new instance of the <see cref="DkimSigningRoutingAgent"/> class.
        /// </summary>
        /// <param name="dkimSigner">The object that knows how to sign messages.</param>
        public DkimSigningRoutingAgent(IDkimSigner dkimSigner)
        {
            if (dkimSigner == null)
            {
                throw new ArgumentNullException("dkimSigner");
            }

            this.dkimSigner = dkimSigner;

            this.OnCategorizedMessage += this.WhenMessageCategorized;
        }
        /// <summary>
        /// Initializes a new instance of the <see cref="DkimSigningRoutingAgent"/> class.
        /// </summary>
        /// <param name="dkimSigner">The object that knows how to sign messages.</param>
        public DkimSigningRoutingAgent(IDkimSigner dkimSigner)
        {
            if (dkimSigner == null)
            {
                throw new ArgumentNullException("dkimSigner");
            }

            this.dkimSigner = dkimSigner;

            this.OnCategorizedMessage += this.WhenMessageCategorized;
        }