Library.System/Common.Library/Email/EmailExtensions.cs

using System.Net.Mail;
using System.Collections.Generic;
using System.Linq;

namespace Common.Library.Email
{
    public static class EmailExtensions
    {
        public static void AddTo(this MailMessage message, List<string> addresses)
        {
            addresses.ForEach(address => message.To.Add(address));
        }

        public static void AddBCC(this MailMessage message, List<string> addresses)
        {
            if(addresses != null && addresses.Count > 0)
            {
                addresses.ForEach(address => message.Bcc.Add(address));
            }
        }

        public static void AddCC(this MailMessage message, List<string> addresses)
        {
            if(addresses != null && addresses.Count > 0)
            {
                addresses.ForEach(address => message.CC.Add(address));
            }
        }
    }
}