Can we access GMAIL API using Service Account?

Question

I have a desktop application to read mail using GMAIL API over REST Interface. I want to use service account so that we can download the mails using domain setting and user

Answer 1

For C# Gmail API v1, you can use the following code to get the gmail service. Use gmail service to read emails. Once you create the service account in Google Console site, download the key file in json format. Assuming the file name is "service.json".

    public static GoogleCredential GetCredenetial(string serviceAccountCredentialJsonFilePath)
    {
        GoogleCredential credential;

        using (var stream = new FileStream(serviceAccountCredentialJsonFilePath, FileMode.Open, FileAccess.Read))
        {
            credential = GoogleCredential.FromStream(stream)
                .CreateScoped(new[] {GmailService.Scope.GmailReadonly})
                .CreateWithUser(**impersonateEmail@email.com**);
        }

        return credential;
    }

    public static GmailService GetGmailService(GoogleCredential credential)
    {
        return new GmailService(new BaseClientService.Initializer()
        {
            HttpClientInitializer = credential,                
            ApplicationName = "Automation App",                
        });
    }

   // how to use
   public static void main()
   {
        var credential = GetCredenetial("service.json");
        var gmailService = GetGmailService(credential);

        // you can use gmail service to retrieve emails. 
        var mMailListRequest = gmailService.Users.Messages.List("me");
        mMailListRequest.LabelIds = "INBOX";

        var mailListResponse = mMailListRequest.Execute();            
   }