C# - Send email using Hotmail, Outlook.com, Office 365¶

App Password and SmtpClientAuthenticationDisabled¶

If your account enabled two-factor authentication, you cannot login your account by normal user authentication, you should create an App Passwords and use this App Password instead of the user password.

You should also check if authenticated client SMTP submission (SMTP AUTH) is enabled:

Enable or disable authenticated client SMTP submission (SMTP AUTH) in Exchange Online.

Last update: Microsoft has disabled App password, you have to switch to Hotmail SMTP OAUTH and Office365 SMTP/EWS/Ms Graph API 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 Hotmail, Outlook.com, Office 365 - example¶

The following example codes demonstrate sending email using Hotmail, Outlook, Office365 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;
using EASendMail; //add EASendMail namespace

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

                // Your email address
                oMail.From = "liveid@hotmail.com";

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

                // Set email subject
                oMail.Subject = "test email from hotmail, outlook, office 365 account";

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

                // Hotmail/Outlook SMTP server address
                SmtpServer oServer = new SmtpServer("smtp.office365.com");

                // If your account is office 365, please change to Office 365 SMTP server
                // SmtpServer oServer = new SmtpServer("smtp.office365.com");

                // User authentication should use your
                // email address as the user name.
                oServer.User = "liveid@hotmail.com";

                // If you got authentication error, try to create an app password instead of your user password.
                // https://support.microsoft.com/en-us/account-billing/using-app-passwords-with-apps-that-don-t-support-two-step-verification-5896ed9b-4263-e681-128a-a6f2979a7944
                oServer.Password = "your password or app password";

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

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

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

                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);
            }
        }
    }
}

Hotmail SMTP OAUTH¶

If your account enabled two-factor authentication, you cannot login your account by normal user authentication, you should use SMTP OAUTH or App Password.

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

Send email from Hotmail/Outlook/Live using user interaction OAuth

Or you can generate App Passwords and use this app password instead of your user password.

Office365 SMTP/EWS/Ms Graph API OAUTH¶

If your account enabled two-factor authentication, you cannot login your account by normal user authentication, you should use SMTP/EWS/Ms Graph API OAUTH or App Password.

Microsoft Office365 SMTP/EWS/Ms Graph API servers have been extended to support authorization via the industry-standard OAuth 2.0 protocol. Using OAUTH protocol, user can do authentication by Microsoft Web OAuth instead of inputting user and password directly in application. This way is more secure, but a little bit complex.

• Send email from Office365 using user interaction OAuth
• Send email from Office365 in background service

Or you can generate App Passwords and use this app password instead of your user password.

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