Changing smtp settings in SwiftMailer dynamically for sending email with multiple form address

I’m using SwiftMailer with SMTP for sending email . I have set user/password settings in module configuration , it works great. But is it possible to change them on runtime ? and also is it possible to add multiple from address for sending email?

Как отправить textbox1.Text через smtp, если он многострочный?

 private void button1_Click(object sender, EventArgs e)     {         MailMessage mail = new MailMessage();         mail.From = new MailAddress("myAddress@yandex.ru"); // Адрес отправителя         mail.To.Add(new MailAddress("clientAddress@mail.ru")); // Адрес получателя         mail.Subject = "Заголовок";         mail.Body = textbox1.Text;          SmtpClient client = new SmtpClient();         client.Host = "smtp.yandex.ru";         client.Port = 587; // Обратите внимание что порт 587         client.EnableSsl = true;         client.Credentials = new NetworkCredential("address@yandex.ru", "password"); // Ваши логин и пароль         client.Send(mail);       } 

Воспользовался этим кодом, но он отправляет только однострочные сообщения, что делать?

My SMTP server appears to be blacklisted and many emails are rejected as spam

The SMTP server provided by my hosting company (159.69.67.92) appears to cause problems – many of my emails sent from this IP address get into the recipient’s spam folder or are rejected by the recipient’s SMTP server.

What are my options for fixing this or using some sort of third-party SMTP server? Except using G Suite (5 USD per month) and except changing the hosting provider.