VB.NET/ASP.NET/ASP MVC - Send email using Microsoft OAuth 2.0 (Modern Authentication) from Hotmail/Outlook account

You can send email using traditional user/password SMTP authentication from personal Hotmail/Outlook account.

However Microsoft will disable traditional user authentication in the future, switching to Microsoft OAuth (Modern Authentication) is strongly recommended now.


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


If you install it by NuGet, no sample projects are installed, only .NET assembly is installed.

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.

add reference in c#/vb.net/c++/cli/clr

.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 1.1, 2.0, 3.5, 4.0, 4.5, 4.6.1, .NET Core 3.1, .NET 5.0, .NET Standard 2.0 and .NET Compact Framework 2.0, 3.5.

File .NET Framework Version
Lib\net20\EASendMail.dll Built with .NET Framework 2.0
It requires .NET Framework 2.0, 3.5 or later version.
Lib\net40\EASendMail.dll Built with .NET Framework 4.0
It requires .NET Framework 4.0 or later version.
Lib\net45\EASendMail.dll Built with .NET Framework 4.5
It requires .NET Framework 4.5 or later version.
Lib\net461\EASendMail.dll Built with .NET Framework 4.6.1
It requires .NET Framework 4.6.1 or later version.
Lib\netcoreapp3.1\EASendMail.dll Built with .NET Core 3.1
It requires .NET Core 3.1 or later version.
Lib\net5.0\EASendMail.dll Built with .NET 5.0
It requires .NET 5.0 or later version.
Lib\net6.0\EASendMail.dll Built with .NET 6.0
It requires .NET 6.0 or later version.
Lib\netstandard2.0\EASendMail.dll Built with .NET Standard 2.0
It requires .NET Standard 2.0 or later version.
Lib\net20-cf\EASendMail.dll Built with .NET Compact Framework 2.0
It requires .NET Compact Framework 2.0, 3.5 or later version.
Lib\net35-cf\EASendMail.dll Built with .NET Compact Framework 3.5
It requires .NET Compact Framework 3.5 or later version.

Create your application in Azure Portal

To use Microsoft/Office365/Live OAuth (Modern Authentication) in your application, you must create a application in Azure Portal.

  • Sign in to the Azure portal using either a work or school account or a personal Microsoft account.
  • If your account gives you access to more than one tenant, select your account in the top right corner, and set your portal session to the Azure AD tenant that you want.

Search Microsoft Entra ID (old name “Azure Active Directory”) and go to this service:

go to azure active directory

Register application

In the left-hand navigation pane, select the Microsoft Entra ID service, and then select App registrations -> New registration.

register app in azure

Input a name to to register the application:

register app in azure

Single tenant and multitenant in account type

When the register an application page appears, enter a meaningful application name and select the account type.

Select which accounts you would like your application to support.

  • If your application only supports the users in your directory or organization, please select Single tenant type;
  • If your application needs to support all users in Office 365 and Microsoft personal account (hotmail.com, outlook.com), please select Multitenant type, and you must verify publisher.

Because we want to support all Office 365 and LIVE SDK (hotmail, outlook personal account), so select Accounts in any organizational directory and personal Microsoft accounts.


If you don’t verify publisher for multitenant application, your application will not request access token successfully.

Assign API permission

Now you need to assign API permission to the application by clicking API Permission -> Add a permission.

add api permission to app in azure

You don’t have to assign all the API permissions below to the application, just assign the API permission(s) you need.

Protocol Permission Scope
Graph API Mail.Send, Mail.ReadWrite https://graph.microsoft.com/Mail.Send, https://graph.microsoft.com/Mail.ReadWrite
EWS EWS.AccessAsUser.All https://outlook.office.com/EWS.AccessAsUser.All
SMTP SMTP.Send https://outlook.office365.com/SMTP.Send
POP POP.AccessAsUser.All https://outlook.office365.com/POP.AccessAsUser.All
IMAP IMAP.AccessAsUser.All https://outlook.office365.com/IMAP.AccessAsUser.All

Now we need to add permission to the application:

  • Click API Permission ->
  • Add a permission -> Microsoft Graph -> Delegated Permission -> User.Read, email, offline_access, openid, profile, SMTP.Send, IMAP.AccessAsUser.All, POP.AccessAsUser.All, Mail.Send, Mail.ReadWrite.
azure application SMTP/POP/IMAP api permission

EWS API permission

With the above permissions, your application can support SMTP, POP, IMAP and Ms Graph API service. If your application needs to support EWS protocol either, add EWS permission like this:

  • Click API Permission ->
  • Add a permission -> APIs in my organization uses -> Office 365 Exchange Online -> Delegated Permission -> Check EWS.AccessAsUser.All
azure APIs in my organization uses

Here is permissions list:

azure application api permission list

Authentication and redirect uri

Because the example code is based on desktop application, so add Redirect Uri like this:

  • Click "Authentication" -> Add a platform -> Mobile and desktop applications -> Redirect Uri, please check or add the following URI.



    • https://login.microsoftonline.com/common/oauth2/nativeclient is used for Live SDK, is used for local Http Listener.
  • If your application needs to support Microsoft personal account, set both "Live SDK Support" and "Treat application as a public client" to "Yes".

azure application Authentication Overview

Client Id and client secrets

Now we need to create a client secret for the application, click Certificates and secrets -> client secrets and add a new client secret.

azure application api permission

After client secret is created, store the client secret value to somewhere.


Please store client secret value by yourself, because it is hidden when you view it at next time.

Branding and verify publisher

Now we click Branding, you can edit your company logo, URL and application name. If your application supports multitenant (access user in all Office 365 and Microsoft personal account), you must complete the publisher verification.

It is not difficult, you can have a look at publisher verification. After publisher verification is completed, your branding is like this:

azure application Authentication Overview


You must complete the publisher verification for multitenant application, otherwise, your application will not request access token correctly.

Client id and tenant

Now you can click Overview to find your client id and tenant.

azure application client id and tenant
  • If your application is single tenant, use the tenant value in tokenUri and authUri instead of common.
  • If your application is multitenant, use common as tenant.

Above client id and client secret support both "Office365 + SMTP/EWS" and "Live (hotmail, outlook personal account) + SMTP".

Enable TLS Strong Encryption Algorithms in .NET 2.0 and .NET 4.0

Because HttpWebRequest is used to get access token from web service. If you’re using .NET framework (.NET 2.0 - 3.5 and .NET 4.x), you need to enable Strong Encryption Algorithms to request access token:

Put the following content to a file named NetStrongEncrypt.reg, right-click this file -> Merge -> Yes. You can also download it from https://www.emailarchitect.net/webapp/download/NetStrongEncrypt.zip.

Windows Registry Editor Version 5.00





Use client id and client secret to request access token

You can use client id and client secret to get the user email address and access token like this:

  • Your application uses a web browser/browser control to open Oauth Url;
  • User inputs user and password in web authentication page, and then the Oauth server returns access token back to your application;
  • Your application uses access token to access resource on the server.
  • You can find full example codes in EASendMail Installation Path\Samples_{Programming language/Developer Tool}\Oauth project.

Access token expiration and refresh token

You don’t have to open browser to request access token every time. By default, access token expiration time is 3600 seconds, you can use the access token repeatedly before it is expired. After it is expired, you can use refresh token to refresh access token directly without opening browser. You can find full sample project in EASendMail installation path to learn how to refresh token.


You should create your client id and client secret, do not use the client id from example codes in production environment, it is used for test purpose. If you got "This app isn't verified" information, please click "Advanced" -> Go to ... for test.

VB.NET - Send email using Microsoft OAuth + Hotmail/Outlook/Live SMTP server

Here is a console application which demonstrates how to use Microsoft OAuth to do user authentication and send email.


This sample cannot handle the event of Web Browser is closed by user manually before authentication is completed. You can refer to the better sample project which uses Web Browser Control in EASendMail installation path.

Imports System
Imports System.IO
Imports System.Net
Imports System.Net.Sockets
Imports System.Threading.Tasks
Imports System.Text
Imports System.Runtime.InteropServices
Imports EASendMail

Module ModuleMsOauthHotmail
    Sub Main(ByVal args As String())
        Console.WriteLine("  Sign in with Microsoft OAuth                                       ")
        Console.WriteLine("   If you got ""This app isn't verified"" information in Web Browser, ")
        Console.WriteLine("   click ""Advanced"" -> Go to ... to continue test.")
        Console.WriteLine("Press any key to sign in...")

            Dim p As MsLiveOauth = New MsLiveOauth()
        Catch ep As Exception
        End Try

    End Sub

    Public Class MsLiveOauth
        Private Sub SendMailWithXOAUTH2(ByVal userEmail As String, ByVal accessToken As String)
            ' Hotmail/Outlook/Live SMTP server address
            Dim oServer As SmtpServer = New SmtpServer("smtp.office365.com")
            ' enable SSL connection
            oServer.ConnectType = SmtpConnectType.ConnectSSLAuto
            ' Using 587 port, you can also use 465 port
            oServer.Port = 587

            ' use SMTP OAUTH 2.0 authentication
            oServer.AuthType = SmtpAuthType.XOAUTH2
            ' set user authentication
            oServer.User = userEmail
            ' use access token as password
            oServer.Password = accessToken

            Dim oMail As SmtpMail = New SmtpMail("TryIt")

            ' Your email address
            oMail.From = userEmail

            ' Please change recipient address to yours for test
            oMail.[To] = "support@emailarchitect.net"
            oMail.Subject = "test email from Hotmail account with OAUTH 2"
            oMail.TextBody = "this is a test email sent from VB.NET project with Hotmail."

            Console.WriteLine("start to send email using OAUTH 2.0 ...")

            Dim oSmtp As SmtpClient = New SmtpClient()
            oSmtp.SendMail(oServer, oMail)

            Console.WriteLine("The email has been submitted to server successfully!")
        End Sub

        ' client configuration
        ' You should create your client id And client secret,
        ' do Not use the following client id in production environment, it Is used for test purpose only.
        Const clientID As String = "eccbabb2-3377-4265-85c1-ea2fb515f075"
        Const clientSecret As String = "QaR_RR:-5WqTY[nni9pdBr9xVybqrAu4"
        Const scope As String = "https://outlook.office.com/SMTP.Send%20offline_access%20email%20openid"
        Const authUri As String = "https://login.microsoftonline.com/common/oauth2/v2.0/authorize"
        Const tokenUri As String = "https://login.microsoftonline.com/common/oauth2/v2.0/token"

        Private Shared Function GetRandomUnusedPort() As Integer
            Dim listener = New TcpListener(IPAddress.Loopback, 0)
            Dim port = (CType(listener.LocalEndpoint, IPEndPoint)).Port
            Return port
        End Function

        Public Async Sub DoOauthAndSendEmail()
            ' Creates a redirect URI using an available port on the loopback address.
            Dim redirectUri As String = String.Format("{0}/", GetRandomUnusedPort())
            Console.WriteLine("redirect URI: " & redirectUri)

            ' Creates an HttpListener to listen for requests on that redirect URI.
            Dim http = New HttpListener()
            Console.WriteLine("Listening ...")

            ' Creates the OAuth 2.0 authorization request.
            Dim authorizationRequest = String.Format("{0}?response_type=code&scope={1}&redirect_uri={2}&client_id={3}&prompt=login",

            ' Opens request in the browser

            ' Waits for the OAuth authorization response.
            Dim context = Await http.GetContextAsync()

            ' Brings the Console to Focus.

            ' Sends an HTTP response to the browser.
            Dim response = context.Response
            Dim responseString As String = String.Format("<html><head></head><body>Please return to the app and close current window.</body></html>")
            Dim buffer = Encoding.UTF8.GetBytes(responseString)
            response.ContentLength64 = buffer.Length
            Dim responseOutput = response.OutputStream
            Dim responseTask As Task = responseOutput.
                WriteAsync(buffer, 0, buffer.Length).
                                Console.WriteLine("HTTP server stopped.")
                            End Sub)

            ' Checks for errors.
            If context.Request.QueryString.[Get]("error") IsNot Nothing Then
                Console.WriteLine(String.Format("OAuth authorization error: {0}.", context.Request.QueryString.[Get]("error")))
            End If

            If context.Request.QueryString.[Get]("code") Is Nothing Then
                Console.WriteLine("Malformed authorization response. " & context.Request.RawUrl)
            End If

            ' extracts the authorization code
            Dim code = context.Request.QueryString.[Get]("code")
            Console.WriteLine("Authorization code: " & code)

            Dim responseText As String = Await RequestAccessToken(code, redirectUri)

            Dim parser As OAuthResponseParser = New OAuthResponseParser()

            Dim user = parser.EmailInIdToken
            Dim accessToken = parser.AccessToken

            Console.WriteLine("User: {0}", user)
            Console.WriteLine("AccessToken: {0}", accessToken)

            SendMailWithXOAUTH2(user, accessToken)
        End Sub

        Private Async Function RequestAccessToken(ByVal code As String, ByVal redirectUri As String) As Task(Of String)
            Console.WriteLine("Exchanging code for tokens...")

            ' builds the  request
            Dim tokenRequestBody = String.Format("code={0}&redirect_uri={1}&client_id={2}&grant_type=authorization_code",

            ' if your application is web application, add clientSecret parameter.
            ' Dim tokenRequestBody = String.Format("code={0}&redirect_uri={1}&client_id={2}&client_secret={3}&grant_type=authorization_code",
            '                code,
            '                Uri.EscapeDataString(redirectUri),
            '                clientID,
            '                clientSecret)

            ' sends the request
            Dim tokenRequest As HttpWebRequest = CType(WebRequest.Create(tokenUri), HttpWebRequest)
            tokenRequest.Method = "POST"
            tokenRequest.ContentType = "application/x-www-form-urlencoded"
            tokenRequest.Accept = "Accept=text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8"

            Dim _byteVersion As Byte() = Encoding.ASCII.GetBytes(tokenRequestBody)
            tokenRequest.ContentLength = _byteVersion.Length
            Dim stream As Stream = tokenRequest.GetRequestStream()
            Await stream.WriteAsync(_byteVersion, 0, _byteVersion.Length)

                ' gets the response
                Dim tokenResponse As WebResponse = Await tokenRequest.GetResponseAsync()

                Using reader As StreamReader = New StreamReader(tokenResponse.GetResponseStream())
                    ' reads response body
                    Return Await reader.ReadToEndAsync()
                End Using

            Catch ex As WebException

                If ex.Status = WebExceptionStatus.ProtocolError Then
                    Dim response = TryCast(ex.Response, HttpWebResponse)

                    If response IsNot Nothing Then
                        Console.WriteLine("HTTP: " & response.StatusCode)

                        ' reads response body
                        Using reader As StreamReader = New StreamReader(response.GetResponseStream())
                            Dim responseText As String = reader.ReadToEnd()
                        End Using
                    End If
                End If

                Throw ex
            End Try
        End Function

        ' Hack to bring the Console window to front.
        Public Sub BringConsoleToFront()
        End Sub

        Private Declare Auto Function GetConsoleWindow Lib "kernel32.dll" () As IntPtr
        Private Declare Auto Function SetForegroundWindow Lib "user32.dll" (ByVal hWnd As IntPtr) As Int32

    End Class

End Module

VB.NET - Send email using Microsoft OAuth + Hotmail/Outlook Live SMTP server in ASP.NET/ASP MVC

If you use Microsoft OAuth in ASP.NET/ASP MVC application, you should use a ASP.NET/ASP MVC page to get authorization code instead of HttpListener. You need to add your ASP.NET/ASP MVC page path to Authentication -> add a platform -> web -> Redirect URIs in your Azure application.

azure application web redirect uri
' if your application is web application, add clientSecret parameter.
Dim tokenRequestBody = String.Format("code={0}&redirect_uri={1}&client_id={2}&client_secret={3}&grant_type=authorization_code",
' Please add http://localhost:54098/oauth/token to Authorized redirect URIs in your Google/MS Azure project.
Public Function Token(ByVal code As String) As ActionResult
    ' code parameter is the authorization code returned by MS OAuth server,
    ' then you can use it to request AccessToken
    ' just like RequestAccessToken method in previous example
End Function

You can find a full sample project in EASendMail installation path\Samples_ASPNetMvc.

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

EA Oauth Service for Office 365

If you are not the tenant administrator and you don’t have the permission to create or grant the application in Azure, or if your code is too complex or out of maintenance, and you don’t want to change anything in your source codes, then you can have a try with EA Oauth Service for Offic365. It provides an easy way for the legacy email application that doesn’t support OAUTH 2.0 to send and retrieve email from Office 365 without changing any codes. SMTP, POP, IMAP and SSL/TLS protocols are supported.



If you have any comments or questions about above example codes, please click here to add your comments.