c# 发送带附件的邮件

using System;
using System.IO;
using System.Net;
using System.Net.Mail;
using System.Net.Mime;
using System.Text;

public class EmailUitls
    {
        /// <summary>
        /// 发送邮件
        /// </summary>
        /// <param name="fileName">附件路径</param>
        /// <param name="name">发件人名字</param>
        /// <param name="eamil">接收邮箱</param>
        /// <param name="title">标题</param>
        /// <param name="content">内容</param>
        /// <returns>成功/失败</returns>
        public static string send(string fileName, string name, string eamil, string title, string content)
        {
            SmtpClient client = new SmtpClient("smtp.qq.com");
            client.EnableSsl = true;
            client.UseDefaultCredentials = false;
            client.Credentials = new System.Net.NetworkCredential("发件人邮箱", "POP3/SMTP服务授权码");

            MailAddress from = new MailAddress("发件人邮箱", name, Encoding.UTF8);//初始化发件人  

            MailAddress to = new MailAddress(eamil, "", Encoding.UTF8);//初始化收件人  

            //设置邮件内容  
            MailMessage message = new MailMessage(from, to);
            message.Body = content.Trim();
            message.BodyEncoding = Encoding.UTF8;
            message.Subject = title.Trim();
            message.SubjectEncoding = Encoding.UTF8;
            message.IsBodyHtml = false;

            if (!string.IsNullOrEmpty(fileName))
            {
                //附件
                Attachment myAttachment = new System.Net.Mail.Attachment(fileName, MediaTypeNames.Application.Octet);

                //MIME协议下的一个对象，用以设置附件的创建时间，修改时间以及读取时间  
                ContentDisposition disposition = myAttachment.ContentDisposition;
                disposition.CreationDate = File.GetCreationTime(fileName);
                disposition.ModificationDate = File.GetLastWriteTime(fileName);
                disposition.ReadDate = File.GetLastAccessTime(fileName);

                //用smtpclient对象里attachments属性，添加上面设置好的myattachment  
                message.Attachments.Add(myAttachment);
            }

            try
            {
                client.Send(message);
                return "邮件发送成功！";
            }
            catch (Exception ex)
            {
                return "邮件发送失败！" + ex.Message;
            }  
        }
    }

 有一个问题，附件太大会发送失败 

 解决方法：https://support.microsoft.com/zh-cn/kb/2468871  （未测试）