ASP.NET MVC中HTML邮件为何以纯文本形式发送？

代码示例 #

MailMessage mail = new MailMessage();
mail.From = new MailAddress(emailFrom);
mail.To.Add(new MailAddress(emailTo));
mail.IsBodyHtml = true;
mail.Subject = subject;
mail.Body = body.ToString();

System.Net.ServicePointManager.ServerCertificateValidationCallback = new System.Net.Security.RemoteCertificateValidationCallback(RemoteServerCertificateValidationCallback);
AlternateView htmlView = AlternateView.CreateAlternateViewFromString(body, Encoding.UTF8, "text/html");
mail.AlternateViews.Add(htmlView);
SmtpClient smtp = new SmtpClient();
smtp.Host = "mail.alpc.ir";
smtp.Port = 25;
smtp.UseDefaultCredentials = false;
smtp.Credentials = new NetworkCredential(emailFrom, emailFromPassword);
smtp.EnableSsl = true;
smtp.DeliveryMethod = SmtpDeliveryMethod.Network;
smtp.Send(mail);

收到的邮件内容 #

p{margin-top: 0;margin-bottom: 0.5rem;}:root{--w1:600px;}:root{--d2:0.5rem;}:root{--fs:12px}@font-face {font-family: iransans;font-style: normal;font-weight: normal;src: url('https://sadidgostaran.ir/Content/IRANSansWeb.woff2') format('woff2');}@media only screen and (max-width:630px){:root{--w1:100%;}}@media only screen and (max-width:420px){:root{--fs:10px}.table-responsive{display: block;width: 100%;overflow-x: auto;-webkit-overflow-scrolling: touch;}}
 گیرنده گرامی  

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 ما را در شبکه های اجتماعی دنبال کنید

سدید گستران در گوگلمحمد مهدی نعمتیسمت شخصسدید گستران امین 021-54942 - 09123456789

info@sadidgostaran.ir

www.sadidgostaran.ir

میدان ولیعصر - ساختمان تجاری ایرانیان - طبقه 4 - واحد 5

解决方案 #

原因分析 #

代码中同时设置了主HTML正文（mail.IsBodyHtml = true + mail.Body）和HTML格式的替代视图（AlternateView），这会导致部分邮件客户端无法正确识别HTML内容，转而以纯文本形式展示。此外，主正文未指定编码，也可能引发解析问题。

修复方案1：移除冗余的AlternateView代码 #

若仅需发送HTML格式邮件，直接使用主正文即可，无需添加AlternateView：

MailMessage mail = new MailMessage();
mail.From = new MailAddress(emailFrom);
mail.To.Add(new MailAddress(emailTo));
mail.IsBodyHtml = true;
mail.Subject = subject;
// 为正文指定UTF-8编码，确保特殊字符正确显示
mail.BodyEncoding = Encoding.UTF8;
mail.Body = body.ToString();

System.Net.ServicePointManager.ServerCertificateValidationCallback = new System.Net.Security.RemoteCertificateValidationCallback(RemoteServerCertificateValidationCallback);

SmtpClient smtp = new SmtpClient();
smtp.Host = "mail.alpc.ir";
smtp.Port = 25;
smtp.UseDefaultCredentials = false;
smtp.Credentials = new NetworkCredential(emailFrom, emailFromPassword);
smtp.EnableSsl = true;
smtp.DeliveryMethod = SmtpDeliveryMethod.Network;
smtp.Send(mail);

修复方案2：同时提供HTML和纯文本版本（推荐） #

为兼容所有邮件客户端，建议同时发送两种格式。主正文设为纯文本，通过AlternateView提供HTML版本：

MailMessage mail = new MailMessage();
mail.From = new MailAddress(emailFrom);
mail.To.Add(new MailAddress(emailTo));
// 主正文为纯文本，IsBodyHtml设为false
mail.IsBodyHtml = false;
mail.Subject = subject;
mail.BodyEncoding = Encoding.UTF8;
// 纯文本内容（可从HTML转换或手动编写）
mail.Body = "这是纯文本版本的邮件内容...";

System.Net.ServicePointManager.ServerCertificateValidationCallback = new System.Net.Security.RemoteCertificateValidationCallback(RemoteServerCertificateValidationCallback);

// 添加HTML格式的替代视图
AlternateView htmlView = AlternateView.CreateAlternateViewFromString(body, Encoding.UTF8, "text/html");
mail.AlternateViews.Add(htmlView);

SmtpClient smtp = new SmtpClient();
smtp.Host = "mail.alpc.ir";
smtp.Port = 25;
smtp.UseDefaultCredentials = false;
smtp.Credentials = new NetworkCredential(emailFrom, emailFromPassword);
smtp.EnableSsl = true;
smtp.DeliveryMethod = SmtpDeliveryMethod.Network;
smtp.Send(mail);

额外注意事项 #

• 确保body变量包含完整且格式正确的HTML代码（如包含<html>、<body>标签，闭合所有标签），不完整的HTML可能被客户端识别为纯文本。
• 测试不同邮件客户端，确保内容显示正常。

内容的提问来源于stack exchange，提问作者meysam rahpeyma