VB.NET/ASP.NET/ASP MVC - Send email using Microsoft OAuth 2.0 (Modern Authentication) + EWS/Ms Graph API protocol from Office 365 in background 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 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.

Office 365 OAuth 2.0 client credentials grant¶

Normal OAuth requires user input user/password for authentication. Obviously, it is not suitable for background service. In this case, You can use the OAuth 2.0 client credentials grant, sometimes called two-legged OAuth, to access web-hosted resources by using the identity of an application. It only works for Office365 user, it doesn’t work for personal Hotmail account.

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.
• In the left-hand navigation pane, select the Azure Active Directory service, and then select App registrations -> New registration.

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 just need to support Offic365 user in our organization, so select Accounts in this organizational directory only (single tenant).

Do not select supporting Microsoft personal account, because there is no way to access Microsoft personal account in background service.

API permissions¶

• Click API Permission -> Microsoft Graph -> Delegated Permission -> User.Read.
• Click API Permission -> Microsoft Graph -> Application Permission -> Mail.Send.
• Click API Permission -> Add a permission -> APIs in my organization uses -> Office 365 Exchange Online -> Application Permission -> Other permission -> full_access_as_app

Here is permissions list:

If your current user is not a user in a verified domain or Offic 365, you will not find Office 365 Exchange Online in API list, then you have to add this API permission manually.

• Select Manifest in the left-hand navigation under Manage.
• Locate the requiredResourceAccess property in the manifest, and add the following inside the square brackets ([]):

{
  "resourceAppId": "00000002-0000-0ff1-ce00-000000000000",
  "resourceAccess": [
      {
          "id": "dc890d15-9560-4a4c-9b7f-a736ec74ec40",
          "type": "Role"
      }
  ]
}

• Select Save.
• Select API permissions under Manage. Confirm that the full_access_as_app permission is listed.

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.

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

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:

Client id and tenant¶

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

Grant admin consent¶

To use your application to access user mailbox in Office365 domain, you should get admin consent by Office365 domain administrator.

• If you created the application and you’re the Office365 administrator:

  In API Permission -> "Click grant admin consent for ..." to grant consent to the application.

• If you created the application and you’re not the Office365 administrator:

  Send the link to Office365 administrator, please change client_id to yours

  https://login.microsoftonline.com/common/adminconsent?client_id=8f54719b-4070-41ae-91ad-f48e3c793c5f&state=12345&redirect_uri=https://login.microsoftonline.com/common/oauth2/nativeclient
  

• Administrator can open above link in web browser, if administrator agrees with the permissions the application requires, grant consent. If not, click cancel or close the window.

• Administrator can change/cancel the permissions by Sign in to the Azure Portal -> Select Azure Active Directory then Enterprise applications.

• After administrator granted consent, web browser will redirect to the following URL, send tenant value to application developer.

  https://login.microsoftonline.com/common/oauth2/nativeclient?admin_consent=True&tenant=79a42c6f-5a9a-439b-a2ca-7aa1b0ed9776&state=12345
  

After administrator authorized the permissions, you can use your application to access any users mailbox in Office365 domain.

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 legacy .NET framework (.NET 2.0 and .NET 4.0), 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

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\.NETFramework\v2.0.50727]
"SystemDefaultTlsVersions"=dword:00000001
"SchUseStrongCrypto"=dword:00000001

[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\.NETFramework\v2.0.50727]
"SystemDefaultTlsVersions"=dword:00000001
"SchUseStrongCrypto"=dword:00000001

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\.NETFramework\v4.0.30319]
"SystemDefaultTlsVersions"=dword:00000001
"SchUseStrongCrypto"=dword:00000001

[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\.NETFramework\v4.0.30319]
"SystemDefaultTlsVersions"=dword:00000001
"SchUseStrongCrypto"=dword:00000001

Access token expiration¶

You don’t have 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.

VB.NET/ASP.NET/ASP MVC - Send email using Microsoft OAuth + EWS from Office 365 account in background service - example¶

Imports  System
Imports  System.Text
Imports  System.Net
Imports  EASendMail

Private Shared Function _postString(ByVal uri As String, ByVal requestData As String) As String
    Dim httpRequest As HttpWebRequest = TryCast(WebRequest.Create(uri), HttpWebRequest)
    httpRequest.Method = "POST"
    httpRequest.ContentType = "application/x-www-form-urlencoded"

    Using requestStream As Stream = httpRequest.GetRequestStream()
        Dim requestBuffer As Byte() = Encoding.UTF8.GetBytes(requestData)
        requestStream.Write(requestBuffer, 0, requestBuffer.Length)
        requestStream.Close()
    End Using

    Try
        Dim httpResponse As HttpWebResponse = TryCast(httpRequest.GetResponse(), HttpWebResponse)
        Using reader As New StreamReader(httpResponse.GetResponseStream())
            Dim responseText = reader.ReadToEnd()
            Return responseText
        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()
                    Console.WriteLine(responseText)
                End Using
            End If
        End If

        Throw ex
    End Try

End Function

Public Sub SendMail()
    Try
        Dim client_id As String = "8f54719b-4070-41ae-91ad-f48e3c793c5f"
        Dim client_secret As String = "cbmYyGQjz[d29wL2ArcgoO7HLwJXL/-."

        ' If your application is not created by Office365 administrator,
        ' please use Office365 directory tenant id, you should ask Offic365 administrator to send it to you.
        ' Office365 administrator can query tenant id in https://portal.azure.com/ - Azure Active Directory.
        Dim tenant As String = "79a42c6f-5a9a-439b-a2ca-7aa1b0ed9776"

        Dim requestData As String = String.Format("client_id={0}&client_secret={1}&scope=https://outlook.office365.com/.default&grant_type=client_credentials",
                            client_id, client_secret)

        Dim tokenUri As String = String.Format("https://login.microsoftonline.com/{0}/oauth2/v2.0/token", tenant)

        Dim responseText As String = _postString(tokenUri, requestData)
        Dim parser As OAuthResponseParser = New OAuthResponseParser()
        parser.Load(responseText)

        Dim officeUser As String = "user@mydomain.onmicrosoft.com"

        Dim server = New SmtpServer("outlook.office365.com")
        server.Protocol = ServerProtocol.ExchangeEWS

        server.User = officeUser
        server.Password = parser.AccessToken

        server.AuthType = SmtpAuthType.XOAUTH2
        server.ConnectType = SmtpConnectType.ConnectSSLAuto

        Dim mail = New SmtpMail("TryIt")
        mail.From = officeUser
        mail.[To] = "support@emailarchitect.net"
        mail.Subject = "Office 365 background service oauth test"
        mail.TextBody = "this is a test, do not reply"

        Dim smtp = New SmtpClient()
        smtp.SendMail(server, mail)
        Console.WriteLine("Message delivered!")

    Catch ep As Exception
        Console.WriteLine(ep.ToString())
    End Try
End Sub

VB.NET/ASP.NET/ASP MVC - Send email using Microsoft OAuth + Ms Graph API from Office 365 account in background service - example¶

Imports  System
Imports  System.Text
Imports  System.Net
Imports  EASendMail

Private Shared Function _postString(ByVal uri As String, ByVal requestData As String) As String
    Dim httpRequest As HttpWebRequest = TryCast(WebRequest.Create(uri), HttpWebRequest)
    httpRequest.Method = "POST"
    httpRequest.ContentType = "application/x-www-form-urlencoded"

    Using requestStream As Stream = httpRequest.GetRequestStream()
        Dim requestBuffer As Byte() = Encoding.UTF8.GetBytes(requestData)
        requestStream.Write(requestBuffer, 0, requestBuffer.Length)
        requestStream.Close()
    End Using

    Try
        Dim httpResponse As HttpWebResponse = TryCast(httpRequest.GetResponse(), HttpWebResponse)
        Using reader As New StreamReader(httpResponse.GetResponseStream())
            Dim responseText = reader.ReadToEnd()
            Return responseText
        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()
                    Console.WriteLine(responseText)
                End Using
            End If
        End If

        Throw ex
    End Try

End Function

Public Sub SendMail()
    Try
        Dim client_id As String = "8f54719b-4070-41ae-91ad-f48e3c793c5f"
        Dim client_secret As String = "cbmYyGQjz[d29wL2ArcgoO7HLwJXL/-."

        ' If your application is not created by Office365 administrator,
        ' please use Office365 directory tenant id, you should ask Offic365 administrator to send it to you.
        ' Office365 administrator can query tenant id in https://portal.azure.com/ - Azure Active Directory.
        Dim tenant As String = "79a42c6f-5a9a-439b-a2ca-7aa1b0ed9776"

        Dim requestData As String = String.Format("client_id={0}&client_secret={1}&scope=https://graph.microsoft.com/.default&grant_type=client_credentials",
                            client_id, client_secret)

        Dim tokenUri As String = String.Format("https://login.microsoftonline.com/{0}/oauth2/v2.0/token", tenant)

        Dim responseText As String = _postString(tokenUri, requestData)
        Dim parser As OAuthResponseParser = New OAuthResponseParser()
        parser.Load(responseText)

        Dim officeUser As String = "user@mydomain.onmicrosoft.com"

        ' Set Offic365 Ms Graph API server address and protocol
        Dim server = New SmtpServer("graph.microsoft.com")
        server.Protocol = ServerProtocol.MsGraphApi

        server.User = officeUser
        server.Password = parser.AccessToken

        server.AuthType = SmtpAuthType.XOAUTH2
        server.ConnectType = SmtpConnectType.ConnectSSLAuto

        Dim mail = New SmtpMail("TryIt")
        mail.From = officeUser
        mail.[To] = "support@emailarchitect.net"
        mail.Subject = "Office 365 background service oauth test"
        mail.TextBody = "this is a test, do not reply"

        Dim smtp = New SmtpClient()
        smtp.SendMail(server, mail)
        Console.WriteLine("Message delivered!")

    Catch ep As Exception
        Console.WriteLine(ep.ToString())
    End Try
End Sub

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

Related links¶

• Send email from Gmail using user interaction OAuth
• Send email from G Suite using service account in background service
• Send email from Hotmail/Outlook/Live using user interaction OAuth
• Send email from Office365 using user interaction OAuth