MailKit.Net.Smtp.SmtpCommandException: 5.5.4 Invalid Email address

Hi Friends,
I developed one tool to send mail from gmail & outlook . it is working fine for gmail but throwing error while sending mail from my outlook email id . smtp settings for outlook I have given as and port 587 got from outlook settings . It is getting authenticated , but while sending mail it throws error as : MailKit.Net.Smtp.SmtpCommandException: 5.5.4 Invalid Email address

Below is my code :
var address = row["email"];
var email = PrepareEmail(emailInstance, row);
if (!client.IsConnected)
//Console.Error.WriteLine("Client disconnected. Exiting. Please resume from email: " + address);
Log.Info("Client disconnected. Exiting. Please resume from email: " + address);
return false;
Console.WriteLine("{0} Sent email to {1}", count, address);
Log.Info(count + " Sent email to " + address);
UpdateExcelData(emailInstance.SpreadsheetPath, row);
return true;
catch (Exception exp)
System.Windows.MessageBox.Show("Unable to send mail for email id: " + address);
return false;
//Prepare email
private MimeMessage PrepareEmail(TDSEmail emailInstance, Dictionary<string, string> row)
var message = new MimeMessage();
message.From.Add(new MailboxAddress(emailInstance.SenderName, emailInstance.FromEmailPassword));
var name = "";
if (row.ContainsKey("name")) name = row["name"];
message.To.Add(new MailboxAddress(name, row["email"]));
message.Subject = emailInstance.EmailSubject;

var builder = new BodyBuilder();
string test = TemplateEngine(row);
builder.HtmlBody = TemplateEngine(row);
builder.HtmlBody = builder.HtmlBody.Replace("${name}",row["name"] );
var attachmentPath = Path.Combine(emailInstance.InputFolder, row["filename"]);
builder.Attachments.Add(row["filename"], File.ReadAllBytes(attachmentPath));
message.Body = builder.ToMessageBody();

return message;