SharePoint Get all users emal from SPUser objec

        public static string strLDAP = "LDAP://Test.com";        public static void GetADMails(ref List<string> list, string strLoginName)        {            DirectoryEntry newEntry = new DirectoryEntry(strLDAP);            strLoginName = strLoginName.Substring(strLoginName.LastIndexOf('\\') + 1);            DirectorySearcher newSearcher = new DirectorySearcher(newEntry, "(&(objectClass=group)(CN=" + strLoginName + "))");            SearchResult sr = newSearcher.FindOne();            if (sr != null)            {                foreach (string srUser in sr.GetDirectoryEntry().Properties["member"])                {                    DirectoryEntry tmpEntry = new DirectoryEntry("LDAP://" + srUser);                    if (tmpEntry.Properties["objectClass"][1].ToString() == "person")                    {                        if (string.IsNullOrEmpty(ConvertNull(tmpEntry.InvokeGet("Mail")).Trim()) || list.Contains(ConvertNull(tmpEntry.InvokeGet("Mail")).Trim()))                        {                            continue;                        }                        Console.WriteLine(tmpEntry.InvokeGet("Mail"));                        list.Add(ConvertNull(tmpEntry.InvokeGet("Mail")).Trim());                    }                    else                    {                        GetADMails(ref list, tmpEntry.InvokeGet("sAMAccountName").ToString());                    }                }            }            else            {                newSearcher = new DirectorySearcher(newEntry, "(&(&(objectCategory=person)(objectClass=user))(cn=" + strLoginName + "))");                sr = newSearcher.FindOne();                if (sr != null)                {                    object obj = sr.Properties["Mail"][0];                    if (!(string.IsNullOrEmpty(ConvertNull(obj).Trim()) || list.Contains(ConvertNull(obj).Trim())))                    {                        list.Add(ConvertNull(obj).Trim());                    }                }            }        }        public static List<string> GetUserMailsByUserField(SPWeb web, object obj)        {            List<string> mailarr = new List<string>();            SPGroup group = null;            if (obj == null)            {                return mailarr;            }            try            {                SPFieldUserValueCollection approversCollection;                web.AllowUnsafeUpdates = true;                approversCollection = (SPFieldUserValueCollection)obj;                foreach (SPFieldUserValue spFieldUserValue in approversCollection)                {                    if (spFieldUserValue.User == null)                    {                        //sharepoitn group                         try                        {                            group = web.SiteGroups[spFieldUserValue.LookupValue];                            SPUserCollection users = group.Users;                            foreach (SPUser user in users)                            {                                if (user.ID == group.Owner.ID)                                {                                    continue;                                }                                if (string.IsNullOrEmpty(ConvertNull(user.Email)))                                {                                    continue;                                }                                if (mailarr.Contains(ConvertNull(user.Email).Trim()))                                {                                    continue;                                }                                mailarr.Add(ConvertNull(user.Email).Trim());                            }                        }                        catch { }                    }                    else                    {                        //sharepoint user or ad group                        try                        {                            GetADMails(ref mailarr, web.AllUsers.GetByID(spFieldUserValue.LookupId).LoginName);                        }                        catch { }                    }                }            }            catch (Exception ex)            {                Console.WriteLine(ex.Message);            }            return mailarr;        }

List<string> maillist= GetUserMailsByUserField(web, item["Reader"]);