C # Failed to send emails using SmtpClient

I'm getting the following error when running the system on the server with port 587: Mailbox not available

Error Stack:

Irunthesamesystemonmylocalmachineanditworksnormallywithport587.

Sourcecodeused:

MailMessagemail=newMailMessage();SmtpClientSmtpServer=newSmtpClient("host");
mail.From = new MailAddress("email");
mail.To.Add("to");
mail.Subject = "teste"
mail.Body = "teste";

SmtpServer.Port = 587;
SmtpServer.Credentials = new 
System.Net.NetworkCredential("login", "senha");
SmtpServer.EnableSsl = false;
SmtpServer.Send(mail);