How to create a Gmail API Message

Question

I'd like to send a Message using Google's Gmail API. I've authenticated successfully, and am trying to use GmailService to send a message.

I'd like to use this:

myService.Users.Messages.Send(myMessage, "me").Execute();

where myService is a Google.Apis.Gmail.v1.GmailService and myMessage is a Google.Apis.Gmail.v1.Data.Message.

myService is fine, I've done the OAuth dance. I can get messages from my Inbox and all that. But I don't know how to construct myMessage. I have a standard .NET MailMessage, with human-readable Subject, Body, To, From etc.

But the Google Message class takes fields Payload or Raw. What's the easiest way to convert a full MailMessage to a string which I can set to the Payload or Raw properties? Or is this not what I should be doing at all?

The documentation for the Message class.

user1002973 · Accepted Answer · 2015-09-28T10:05:30.867

I found a solution. Strangely, .NET doesn't seem to support this natively/easily. There's a nice nuget package though, called AE.Net.Mail, which can write an easy-to-create message object to a stream.

Here's the sample code that pointed me in that direction.

Copy-and-pasted code as site seems to be down, and Google's cache might not last forever:

using System.IO;
using System.Net.Mail;
using Google.Apis.Gmail.v1;
using Google.Apis.Gmail.v1.Data;

public class TestEmail {

  public void SendIt() {
    var msg = new AE.Net.Mail.MailMessage {
      Subject = "Your Subject",
      Body = "Hello, World, from Gmail API!",
      From = new MailAddress("[you]@gmail.com")
    };
    msg.To.Add(new MailAddress("yourbuddy@gmail.com"));
    msg.ReplyTo.Add(msg.From); // Bounces without this!!
    var msgStr = new StringWriter();
    msg.Save(msgStr);

    var gmail = new GmailService(Context.GoogleOAuthInitializer);
    var result = gmail.Users.Messages.Send(new Message {
      Raw = Base64UrlEncode(msgStr.ToString())
    }, "me").Execute();
    Console.WriteLine("Message ID {0} sent.", result.Id);
  }

  private static string Base64UrlEncode(string input) {
    var inputBytes = System.Text.Encoding.UTF8.GetBytes(input);
    // Special "url-safe" base64 encode.
    return Convert.ToBase64String(inputBytes)
      .Replace('+', '-')
      .Replace('/', '_')
      .Replace("=", "");
  }
}

For anyone looking at this in the future, make sure you are using the `AE.Net.Mail` Nuget Package (https://www.nuget.org/packages/AE.Net.Mail/) and not `System.Net.Mail` (https://msdn.microsoft.com/en-us/library/system.net.mail(v=vs.110).aspx). They are *very* similar, but work slightly differently (e.g. `System.Net.Mail.MailMessage` doesn't have the `Save` method) — derekantrican, Jun 09 '17 at 19:26

score 4 · Answer 2 · edited May 23 '17 at 10:31

Here is an alternative version using using MimeKit.

public void SendEmail(MyInternalSystemEmailMessage email)
{
    var mailMessage = new System.Net.Mail.MailMessage();
    mailMessage.From = new System.Net.Mail.MailAddress(email.FromAddress);
    mailMessage.To.Add(email.ToRecipients);
    mailMessage.ReplyToList.Add(email.FromAddress);
    mailMessage.Subject = email.Subject;
    mailMessage.Body = email.Body;
    mailMessage.IsBodyHtml = email.IsHtml;

    foreach (System.Net.Mail.Attachment attachment in email.Attachments)
    {
        mailMessage.Attachments.Add(attachment);
    }

    var mimeMessage = MimeKit.MimeMessage.CreateFromMailMessage(mailMessage);

    var gmailMessage = new Google.Apis.Gmail.v1.Data.Message {
        Raw = Encode(mimeMessage.ToString())
    };

    Google.Apis.Gmail.v1.UsersResource.MessagesResource.SendRequest request = service.Users.Messages.Send(gmailMessage, ServiceEmail);

    request.Execute();
}

public static string Encode(string text)
{
    byte[] bytes = System.Text.Encoding.UTF8.GetBytes(text);

    return System.Convert.ToBase64String(bytes)
        .Replace('+', '-')
        .Replace('/', '_')
        .Replace("=", "");
}

Note: If you are getting an email bounce issue, it is likely due to not setting the ReplyToList field. See: GMail API Emails Bouncing

score 2 · Answer 3 · answered Sep 18 '18 at 10:42

C# Code for Gmail API Message (send email)

   namespace GmailAPIApp
   {
        class SendMail
        {
              static string[] Scopes = { GmailService.Scope.GmailSend };
              static string ApplicationName = "Gmail API .NET Quickstart";

             static void Main(string[] args)
             {
                UserCredential credential;

                using (var stream =
                new FileStream("credentials_dev.json", FileMode.Open, 
                  FileAccess.Read))
                {
                   string credPath = "token_Send.json";
                   credential = GoogleWebAuthorizationBroker.AuthorizeAsync(
                                GoogleClientSecrets.Load(stream).Secrets,
                                 Scopes,
                                 "user",
                                 CancellationToken.None,
                                 new FileDataStore(credPath, true)).Result;
                 Console.WriteLine("Credential file saved to: " + credPath);
               }

        // Create Gmail API service.
        var service = new GmailService(new BaseClientService.Initializer()
        {
            HttpClientInitializer = credential,
            ApplicationName = ApplicationName,
        });

        // Define parameters of request.           
        string plainText = "To:xxxx@gmail.com\r\n" +
                         "Subject: Gmail Send API Test\r\n" +
                         "Content-Type: text/html; charset=us-ascii\r\n\r\n" +
                         "<h1>TestGmail API Testing for sending <h1>";                          

        var newMsg = new Google.Apis.Gmail.v1.Data.Message();
        newMsg.Raw = SendMail.Base64UrlEncode(plainText.ToString());
        service.Users.Messages.Send(newMsg, "me").Execute();
        Console.Read();
    }
    private static string Base64UrlEncode(string input)
    {
        var inputBytes = System.Text.Encoding.UTF8.GetBytes(input);
        // Special "url-safe" base64 encode.
        return Convert.ToBase64String(inputBytes)
          .Replace('+', '-')
          .Replace('/', '_')
          .Replace("=", "");
        }
    }   
 }

score -1 · Answer 4 · answered Apr 26 '19 at 09:10

This is the code that worked for me:

Private Async Sub BtnSendGmail_Click(sender As Object, e As EventArgs) Handles BtnSendGmail.Click

    Try
        Dim credential As UserCredential = Await GoogleWebAuthorizationBroker.AuthorizeAsync(New ClientSecrets With {
            .ClientId = "---------Your ClientId------------",
            .ClientSecret = "----------Your ClientSecret-----------"
        }, {GmailService.Scope.GmailSend}, "user", CancellationToken.None, New FileDataStore(Me.GetType().ToString()))

        Dim service = New GmailService(New BaseClientService.Initializer() With {
            .HttpClientInitializer = credential,
            .ApplicationName = Me.GetType().ToString()
        })

        Dim plainText As String = "From: sender@gmail.com" & vbCrLf &
                                  "To: dest1@gmail.com," & "dest2@gmail.com" & vbCrLf &
                                  "Subject: This is the Subject" & vbCrLf &
                                  "Content-Type: text/html; charset=us-ascii" & vbCrLf & vbCrLf &
                                  "This is the message text."

        Dim newMsg = New Google.Apis.Gmail.v1.Data.Message With {
            .Raw = EncodeBase64(plainText.ToString())
        }
        service.Users.Messages.Send(newMsg, "me").Execute()

        MessageBox.Show("Message Sent OK")
    Catch ex As Exception
        MessageBox.Show("Message failed :" & vbCrLf & "Source: " & ex.Source & vbCrLf & "HResult: " & ex.HResult & vbCrLf & "Message: " &
                        ex.Message & vbCrLf & "StackTrace: " & ex.StackTrace)
    End Try
End Sub


Public Shared Function EncodeBase64(ByVal text As String) As String
    ' Encodes a text-string for sending as an email message
    Dim bytes As Byte() = System.Text.Encoding.UTF8.GetBytes(text)
    Return System.Convert.ToBase64String(bytes).Replace("+"c, "-"c).Replace("/"c, "_"c).Replace("=", "")
End Function

How to create a Gmail API Message

4 Answers4

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