发送邮件失败,显示 Base64字符数组的无效长度
winform程序,发送邮件失败，邮箱是163企业邮箱，但是在foxmail中能发送！
如果换成另外一个163免费邮箱，就没问题！！
代码如下
=======================================
using System.Net.Mail;

try
{
SmtpClient client = new SmtpClient();
client.Host = "smtp.163vip.com";
client.Port = 25;

client.UseDefaultCredentials = false;
client.Credentials = new System.Net.NetworkCredential("myemial01@shieldwood.com", "*****");
client.DeliveryMethod = SmtpDeliveryMethod.Network;

MailMessage mail = new MailMessage();
mail.Subject = "subject";
MailAddress from = new MailAddress("myemial01@shieldwood.com", "myemial01@shieldwood.com");
mail.From = from;

mail.Body = "email body";
mail.SubjectEncoding = System.Text.Encoding.Default;
mail.BodyEncoding = System.Text.Encoding.Default;
mail.Priority = MailPriority.Normal;
mail.DeliveryNotificationOptions = DeliveryNotificationOptions.OnSuccess;

client.Send(mail);

}
catch (Exception ex)
{
string strErr = ex.Message;
if (ex.InnerException != null)
  strErr = strErr + "\r\n\r\n" + ex.InnerException.Message; //这里Base64字符数组的无效长度

//strErr 显示： 发送邮件失败 Base64字符数组的无效长度
}

搞不懂，不知怎么回事！

------解决方案--------------------
内容
public string EncodeString(string content)
{
byte[] encrypted = Convert.FromBase64String(content);
return System.Text.ASCIIEncoding.Default.GetString(encrypted);
}


------解决方案--------------------
长度必须是4的倍数