public IRecipientOption AddCustomArguments(string key, string value)
        {
            if (CustomArguments == null)
            {
                CustomArguments = new Dictionary <string, string>();
            }

            CustomArguments.Add(key, value);
            return(this);
        }
        public ISendEmailCommand AddCustomArguments(string key, string value)
        {
            if (CustomArguments == null)
            {
                CustomArguments = new Dictionary <string, string>();
            }

            CustomArguments.Add(key, value);
            return(this);
        }