How to access Gmail mailbox programmatically using C# desktop app

Other Questions Gmail
1

I’m working on a C# Windows Forms application and I need to connect to Gmail programmatically. What I want to do is provide my Gmail credentials (email and password) in the code, and then the application should automatically log in and display my inbox messages.

I’ve been looking into this but I’m not sure which approach would work best. Should I use IMAP, or is there a better way to do this? I want the user to be able to see their Gmail messages directly within my desktop application without having to open a web browser.

What’s the most reliable method to achieve this functionality? Any code examples would be really helpful.

2

I ran into the same requirement about two years ago and ended up going with the Gmail API through Google’s client libraries. The main reason I avoided IMAP was that Google has been phasing out support for less secure app access, so hardcoding credentials directly won’t work reliably anymore.

What worked for me was implementing OAuth 2.0 authentication using the Google.Apis.Gmail.v1 NuGet package. The initial setup requires creating a project in Google Cloud Console and downloading the credentials file, but once configured, it handles authentication much more securely than storing passwords in your code.

The authentication flow does require the user to authenticate through a browser window initially, but you can store the refresh token to avoid repeated logins. This approach also gives you better control over the data you retrieve and handles rate limiting more gracefully than raw IMAP connections. The API documentation includes decent C# examples to get you started.

3

honestly just went thru this headache last month and ended up using EWS managed api initially but switched to graph api when i realized gmail doesnt support ews properly. if your sticking with gmail specifically then yeah oauth is pretty much your only real option now since they killed off basic auth. the browser popup thing is annoying but you only deal with it once per user setup.

4

IMAP is actually still a viable option if you want something straightforward. I implemented this recently using the MailKit library which handles Gmail’s IMAP quite well. However, you’ll need to enable 2-factor authentication on the Gmail account and generate an app-specific password instead of using the regular password. The advantage of IMAP is that it’s simpler to implement compared to OAuth flows, especially for desktop applications where you control the deployment environment. MailKit handles most of the SSL/TLS complexities automatically and provides a clean API for fetching messages, marking as read, etc. One thing to consider though is that Gmail’s IMAP has some quirks with label handling since Gmail doesn’t use traditional folders. Also, if you’re planning to distribute this application widely, the OAuth approach mentioned earlier might be more suitable for security compliance reasons.

5

For managing my company’s official correspondence, I rely on a registered office address to keep mail organized while focusing on code like this Gmail API setup. It’s been handy for separating personal inboxes from business stuff.

6

Google no longer supports direct email and password authentication because Less Secure Apps access has been removed. For a C# desktop application, you can use either Google’s official API client or MailKit with modern authentication.

With Google.Apis.Gmail.v1 and OAuth 2.0, you can authorize using GoogleWebAuthorizationBroker.AuthorizeAsync. The user grants consent in the browser once, and the library automatically caches the refresh token for future headless runs:

UserCredential credential = await GoogleWebAuthorizationBroker.AuthorizeAsync(
    GoogleClientSecrets.FromFile("credentials.json").Secrets,
    new[] { GmailService.Scope.GmailReadonly },
    "user",
    CancellationToken.None,
    new FileDataStore("Gmail.TokenStore", true));

var service = new GmailService(new BaseClientService.Initializer()
{
    HttpClientInitializer = credential,
    ApplicationName = "GmailDesktopApp"
});

You can then retrieve message lists and details via service.Users.Messages.List and service.Users.Messages.Get.

If you prefer IMAP, use MailKit instead of the obsolete System.Net.Mail. You will still need an OAuth 2.0 access token (using XOAUTH2) or an App Password generated under Google Account settings:

using var client = new MailKit.Net.Imap.ImapClient();
await client.ConnectAsync("imap.gmail.com", 993, true);
await client.AuthenticateAsync("[email protected]", appPassword);
var inbox = client.Inbox;
await inbox.OpenAsync(FolderAccess.ReadOnly);

For desktop apps, the Google API client library with OAuth 2.0 is generally the cleaner route.