如何使用 MailMessage 通过 SendGrid 发送邮件？

Question

我正在尝试使用 SendGrid 发送邮件，但我不能。它总是抛出一个我无法修复的异常。

我该如何解决这个问题？

发送邮件

public static Boolean isSend(IList<String> emailTo, String mensagem, String assunto, String emailFrom, String emailFromName){        
        try{            
            MailMessage mail = new MailMessage();
            mail.BodyEncoding = System.Text.Encoding.UTF8;
            mail.SubjectEncoding = System.Text.Encoding.UTF8;
            //to
            foreach (String e in emailTo) {
                mail.To.Add(e);
            }             
            mail.From = new MailAddress(emailFrom);
            mail.Subject = assunto;            
            mail.Body = mensagem;
            mail.IsBodyHtml = true;
            SmtpClient smtp = new SmtpClient();
            smtp.Host = CustomEmail.SENDGRID_SMTP_SERVER;
            smtp.Port = CustomEmail.SENDGRID_PORT_587;            
            smtp.Credentials = new System.Net.NetworkCredential(CustomEmail.SENDGRID_API_KEY_USERNAME, CustomEmail.SENDGRID_API_KEY_PASSWORD);
            smtp.UseDefaultCredentials = false;
            smtp.EnableSsl = false;
            smtp.Timeout = 20000;
            smtp.Send(mail);
            return true;
        }catch (SmtpException e){
            Debug.WriteLine(e.Message);
            return false;
        }        
    }

自定义邮件

//SendGrid Configs   
    public const String SENDGRID_SMTP_SERVER = "smtp.sendgrid.net";
    public const int SENDGRID_PORT_587 = 587;
    public const String SENDGRID_API_KEY_USERNAME = "apikey"; //myself
    public const String SENDGRID_API_KEY_PASSWORD = "SG.xx-xxxxxxxxxxxxxxxxxxxxxxxxx-E";

异常

Exception thrown: 'System.Net.Mail.SmtpException' in System.dll
Server Answer: Unauthenticated senders not allowed

Answer 1

要使用 SendGrid 发送电子邮件，有 v3 API. The NuGet name is SendGrid and the link is here。

此库不适用于 System.Net.Mail.MailMessage，它使用 SendGrid.Helpers.Mail.SendGridMessage。

此库使用 API 密钥进行授权。您可以在登录 SendGrid 网络应用程序时创建一个，然后导航至电子邮件 API -> 集成指南 -> Web API -> C#。

var client = new SendGridClient(apiKey);
var msg = MailHelper.CreateSingleTemplateEmail(from, new EmailAddress(to), templateId, dynamicTemplateData);

try
{
    var response = client.SendEmailAsync(msg).Result;
    if (response.StatusCode != HttpStatusCode.OK
        && response.StatusCode != HttpStatusCode.Accepted)
    {
        var errorMessage = response.Body.ReadAsStringAsync().Result;
        throw new Exception($"Failed to send mail to {to}, status code {response.StatusCode}, {errorMessage}");
    }
}
catch (WebException exc)
{
    throw new WebException(new StreamReader(exc.Response.GetResponseStream()).ReadToEnd(), exc);
}

Answer 2

我认为你的问题源于没有在构造函数中用服务器实例化 SMTP 客户端。此外，您应该将 smtpclient 包装在 using 语句中，以便正确处理它，或者在完成后调用 dispose。

试试这个：

    public static Boolean isSend(IList<String> emailTo, String mensagem, String assunto, String emailFrom, String emailFromName)
    {
        try
        {
            MailMessage mail = new MailMessage();
            mail.BodyEncoding = System.Text.Encoding.UTF8;
            mail.SubjectEncoding = System.Text.Encoding.UTF8;
            //to
            foreach (String e in emailTo)
            {
                mail.To.Add(e);
            }
            mail.From = new MailAddress(emailFrom);
            mail.Subject = assunto;
            mail.Body = mensagem;
            mail.IsBodyHtml = true;
            using(SmtpClient smtp = new SmtpClient(CustomEmail.SENDGRID_SMTP_SERVER)){
                smtp.Port = CustomEmail.SENDGRID_PORT_587;
                smtp.Credentials = new System.Net.NetworkCredential(CustomEmail.SENDGRID_API_KEY_USERNAME, CustomEmail.SENDGRID_API_KEY_PASSWORD);
                smtp.UseDefaultCredentials = false;
                smtp.EnableSsl = false;
                smtp.Timeout = 20000;
                smtp.Send(mail)
            }
        }
        catch (SmtpException e)
        {
            Debug.WriteLine(e.Message);
            return false;
        }
    }

如果这不起作用，您可以尝试删除 smtp 客户端的端口、enablessl 和 usedefaultcredentials 参数。我一直使用 sendgrid 并且不使用这些选项。

Answer 3

为了更具体地回答您最初的问题和异常原因，SendGrid SMTP 服务器可能不是在寻找您帐户的用户名和密码，而是在寻找您的 API 密钥。该错误似乎表明您的身份验证不成功。

https://sendgrid.com/docs/for-developers/sending-email/v3-csharp-code-example/

To integrate with SendGrids SMTP API:

Create an API Key with at least "Mail" permissions.

Set the server host in your email client or application to smtp.sendgrid.net.

This setting is sometimes referred to as the external SMTP server or the SMTP relay.

Set your username to apikey.

Set your password to the API key generated in step 1.

Set the port to 587.

使用 SendGrid C# 库也将简化此过程：

https://sendgrid.com/docs/for-developers/sending-email/v3-csharp-code-example/

// using SendGrid's C# Library
// https://github.com/sendgrid/sendgrid-csharp
using SendGrid;
using SendGrid.Helpers.Mail;
using System;
using System.Threading.Tasks;

namespace Example
{
    internal class Example
    {
        private static void Main()
        {
            Execute().Wait();
        }

        static async Task Execute()
        {
            var apiKey = Environment.GetEnvironmentVariable("NAME_OF_THE_ENVIRONMENT_VARIABLE_FOR_YOUR_SENDGRID_KEY");
            var client = new SendGridClient(apiKey);
            var from = new EmailAddress("test@example.com", "Example User");
            var subject = "Sending with SendGrid is Fun";
            var to = new EmailAddress("test@example.com", "Example User");
            var plainTextContent = "and easy to do anywhere, even with C#";
            var htmlContent = "<strong>and easy to do anywhere, even with C#</strong>";
            var msg = MailHelper.CreateSingleEmail(from, to, subject, plainTextContent, htmlContent);
            var response = await client.SendEmailAsync(msg);
        }
    }
}

如何使用 MailMessage 通过 SendGrid 发送邮件？

How do I to use MailMessage to send mail using SendGrid?

c#

asp.net-mvc

sendgrid