C# - Send email using Gmail SMTP server¶

Gmail App Password¶

To help keep your account secure, starting May 30, 2022, ​​Google will no longer support the use of third-party apps or devices which ask you to sign in to your Google Account using only your username and password.

Therefore, you should sign in using App Passwords. An App Password is a 16-digit passcode that gives a less secure app or device permission to access your Google Account. App Passwords can only be used with accounts that have 2-Step Verification turned on. You need to use App Password instead of the user password for user authentication.

Another solution is Gmail OAUH, please see Gmail SMTP OAUTH section.

Last update: Google has disabled App password, you have to switch to Gmail SMTP OAUTH. If you don’t want to change your code, you can have a try with EA Oauth Service.

Installation¶

Before you can use the following codes, please download EASendMail SMTP Component and install it on your machine at first. Full sample proejcts are included in this installer.

Install from NuGet

You can also install the run-time assembly by NuGet. Run the following command in the NuGet Package Manager Console:

Install-Package EASendMail

Add reference¶

To use EASendMail SMTP Component in your project, the first step is Add reference of EASendMail to your project. Please create or open your project with Visual Studio, then go to menu -> Project -> Add Reference -> .NET -> Browse..., and select Installation Path\Lib\net[version]\EASendMail.dll from your disk, click Open -> OK, the reference of EASendMail will be added to your project, and you can start to use it to send email in your project.

.NET assembly¶

Because EASendMail has separate builds for .Net Framework, please refer to the following table and choose the correct dll.

Separate builds of run-time assembly for .NET Framework 2.0, 3.5, 4.0, 4.5, 4.6.1, 4.7.2, 4.8.1, .NET 5.0, .NET 6.0, .NET 7.0, .NET 8.0, .NET Standard 2.0 and .NET Compact Framework 2.0, 3.5.

C# - Send email using Gmail SMTP server - example¶

The following example codes demonstrate sending email using Gmail SMTP server. In order to run it correctly, please change SMTP server, user, password, sender, recipient value to yours.

using System;
using System.Collections.Generic;
using System.Text;

// Add EASendMail namespace
using EASendMail;

namespace mysendemail
{
    class Program
    {
        static void Main(string[] args)
        {
            try
            {
                SmtpMail oMail = new SmtpMail("TryIt");

                // Your gmail email address
                oMail.From = "gmailid@gmail.com";

                // Set recipient email address
                oMail.To = "support@emailarchitect.net";

                // Set email subject
                oMail.Subject = "test email from gmail account";

                // Set email body
                oMail.TextBody = "this is a test email sent from c# project with gmail.";

                // Gmail SMTP server address
                SmtpServer oServer = new SmtpServer("smtp.gmail.com");

                // Gmail user authentication
                // For example: your email is "gmailid@gmail.com", then the user should be the same
                oServer.User = "gmailid@gmail.com";

                // Create app password in Google account
                // https://support.google.com/accounts/answer/185833?hl=en
                oServer.Password = "your app password";

                // If you want to use direct SSL 465 port,
                // please add this line, otherwise TLS will be used.
                // oServer.Port = 465;

                // set 587 TLS port;
                oServer.Port = 587;

                // detect SSL/TLS automatically
                oServer.ConnectType = SmtpConnectType.ConnectSSLAuto;

                Console.WriteLine("start to send email over SSL ...");

                SmtpClient oSmtp = new SmtpClient();
                oSmtp.SendMail(oServer, oMail);

                Console.WriteLine("email was sent successfully!");
            }
            catch (Exception ep)
            {
                Console.WriteLine("failed to send email with the following error:");
                Console.WriteLine(ep.Message);
            }
        }
    }
}

Gmail SMTP OAUTH¶

The Gmail IMAP and SMTP servers have been extended to support authorization via the industry-standard OAuth 2.0 protocol. Using OAUTH protocol, user can do authentication by Gmail Web OAuth instead of inputting user and password directly in application. This way is more secure, but a little bit complex.

• Send email from Gmail using user interaction OAuth
• Send email from G Suite using service account in background service

TLS 1.2 protocol¶

TLS is the successor of SSL, more and more SMTP servers require TLS 1.2 encryption now.

If your operating system is Windows XP/Vista/Windows 7/Windows 2003/2008/2008 R2/2012/2012 R2, you need to enable TLS 1.2 protocol in your operating system like this:

Enable TLS 1.2 on Windows XP/Vista/7/10/Windows 2008/2008 R2/2012