1. Home
  2. EAGetMail POP3/IMAP4 Component
  3. KB
  4. Example Codes
  5. VB.NET
  6. VB.NET - Retrieve Email using Microsoft OAuth 2.0 (Modern Authentication) + EWS Protocol from Office 365 in Background Service

Tutorial Index

VB.NET/ASP.NET/ASP MVC - Retrieve email using Microsoft OAuth 2.0 + EWS/Graph API/IMAP4/POP3 protocol from Office 365 in background service

You can retrieve email using traditional user/password authentication from Office 365 account by EWS/IMAP/POP3 Protocol.

However Microsoft has disabled traditional user authentication in many tenants, switching to Microsoft OAuth (Modern Authentication) is strongly recommended now.

In this topic, I will introduce how to retrieve email using VB.NET and Microsoft OAuth (Modern Authentication) in background service.

Installation

Before you can use the following sample codes, you should download the EAGetMail Installer and install it on your machine at first. Full sample projects 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 EAGetMail

Note

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

Add reference

To use EAGetMail POP3 & IMAP Component in your project, the first step is “Add reference of EAGetMail 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\[netversion]\EAGetMail.dll, click Open-> OK, the reference will be added to the project, you can start to use it to retrieve email and parse email in your project.

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

.NET assembly

Because EAGetMail 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, 4.0, 4.5, 4.6.1, 4.7.2, 4.8.1, .NET 6.0, NET 7.0, .NET 8.0, .NET Standard 2.0 and .Net Compact Framework 2.0, 3.5.

File .NET Framework Version
Lib\[net20|40|45|461|472|481]\EAGetMail.dll Built with .NET Framework 2.0, 4.0, 4.5, 4.6.1, 4.7.2, 4.8.1
It requires .NET Framework 2.0, 3.5 or later version.
Lib\[net5.0|6.0|7.0|8.0]\EAGetMail.dll Built with .NET 5.0, .NET 6.0, .NET 7.0, .NET 8.0
It requires .NET 5.0 or later version.
Lib\netstandard2.0\EAGetMail.dll Built with .NET Standard 2.0
It requires .NET Standard 2.0 or later version.
Lib\[net20-cf|net35-cf]\EAGetMail.dll Built with .NET Compact Framework 2.0, 3.5
It requires .NET Compact Framework 2.0, 3.5 or later version.

Office 365 OAuth 2.0 client credentials grant

Normal OAuth requires user to input user and password in browser for authentication. Obviously, it is not suitable for background service.

The solution is granting admin consent to the azure application, then the application can use the client secret value to request the access token directly. This way doesn’t require user attending, it is suitable for background service.

This tutorial introduces how to register application for background service in Azure Portal, then assign the Graph API/EWS/SMTP/POP/IMAP API permission to the application and add the access right to the mailbox of specific user.

Register the application in Azure Portal

Sign in to the Azure Portal using the Microsoft account of the Office 365 administrator. 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

Find the application id (client id) and tenant id

After the application is registered, you can click Overview to find the client id and tenant id. These are required parameters for requesting access token.

client int of azure app

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/.default
EWS full_access_as_app https://outlook.office365.com/.default
SMTP SMTP.AccessAsApp https://outlook.office365.com/.default
POP POP.AccessAsApp https://outlook.office365.com/.default
IMAP IMAP.AccessAsApp https://outlook.office365.com/.default

Graph API permission

Go to Microsoft APIs -> Microsoft Graph -> Application Permission ->

add graph api permission to app in azure

Add Mail.Send and Mail.ReadWrite permission

add Graph Mail.Send Mail.ReadWrite permission to app in azure

EWS and SMTP/POP/IMAP permission

Go to APIs in my organization uses -> Office 365 Exchange Online -> Application Permission ->

add exchange online permission to app in azure

Add full_access_app permission

add exchange online EWS permission to app in azure

Add POP.AccessAsApp permission

add exchange online POP permission to app in azure

Add IMAP.AccessAsApp permission

add exchange online IMAP permission to app in azure

Add SMTP.AccessAsApp permission

add exchange online SMTP permission to app in azure

Complete permissions list

api permission overview in azure

Create client secret

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

add client secret in azure add client secret in azure

Store client secret value

After client secret is created, store the client secret value to somewhere. It is another required parameter for requesting access token.

copy client secret value

Important

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

Now you can use the client id, tenant id and client secret value to request access token. But to use SMTP/POP/IMAP protocol, you need to Register SMTP/POP/IMAP service principals in Exchange as well.

Important

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.

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 - .NET 3.5 and .NET 4.0 - 4.6.1), 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

Now you can use the following example codes to retrieve email with Graph API or EWS protocol:

VB.NET/ASP.NET/ASP MVC - Retrieve email using Graph API + Microsoft OAuth 2.0 in background service - example

Imports System
Imports System.Text
Imports System.IO
Imports System.Net
Imports System.Globalization
Imports EAGetMail

Function _generateFileName(ByVal sequence As Integer) As String
    Dim currentDateTime As DateTime = DateTime.Now
    Return String.Format("{0}-{1:000}-{2:000}.eml",
                    currentDateTime.ToString("yyyyMMddHHmmss", New CultureInfo("en-US")),
                    currentDateTime.Millisecond,
                    sequence)
End Function

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 RetrieveEmail()
    Try
        Dim client_id As String = "b22194da-44d6-4320-a067-e86a275d6fa4"
        Dim client_secret As String = "VTO8Q~eo0JCXc291jcM4wnhZ_GXyKMu."

        ' 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 = "2ea4955d-830e-4aa7-8ab5-661a6b9aa84d"

        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"

        ' Create a folder named "inbox" under current directory
        ' to save the email retrieved.
        Dim localInbox As String = String.Format("{0}\inbox", Directory.GetCurrentDirectory())

        ' If the folder is not existed, create it.
        If Not Directory.Exists(localInbox) Then
            Directory.CreateDirectory(localInbox)
        End If

        ' Office 365 Graph API address, use access token as password
        Dim oServer As New MailServer("graph.microsoft.com",
                officeUser,
                parser.AccessToken,
                ServerProtocol.MsGraphApi) ' Use Http Graph API Protocol

        ' User OAUTH 2.0
        oServer.AuthType = ServerAuthType.AuthXOAUTH2
        ' Enable SSL/TLS connection,
        oServer.SSLConnection = True

        Console.WriteLine("Connecting {0} ...", oServer.Server)

        Dim oClient As New MailClient("TryIt")
        oClient.Connect(oServer)

        ' Get New email only, if you want to get all emails, please remove this line
        oClient.GetMailInfosParam.GetMailInfosOptions = GetMailInfosOptionType.NewOnly

        Dim infos As MailInfo() = oClient.GetMailInfos()
        Console.WriteLine("Total {0} email(s)", infos.Length)

        For i As Integer = 0 To infos.Length - 1
            Dim info As MailInfo = infos(i)
            Console.WriteLine("Index: {0}; Size: {1}; UIDL: {2}",
                info.Index, info.Size, info.UIDL)

            ' Retrieve email from email server
            Dim oMail As Mail = oClient.GetMail(info)

            Console.WriteLine("From: {0}", oMail.From.ToString())
            Console.WriteLine("Subject: {0}" & vbCr & vbLf, oMail.Subject)

            ' Generate an unqiue email file name based on date time.
            Dim fileName As String = _generateFileName(i + 1)
            Dim fullPath As String = String.Format("{0}\{1}", localInbox, fileName)

            ' Save email to local disk
            oMail.SaveAs(fullPath, True)

            ' Mark email as read to prevent retrieving this email again.
            oClient.MarkAsRead(info, True)

            ' If you want to delete current email, please use Delete method instead of MarkAsRead
            ' oClient.Delete(info)

        Next

        ' Quit and expunge emails marked as deleted from  server.
        oClient.Quit()
        Console.WriteLine("Completed!")

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

VB.NET/ASP.NET/ASP MVC - Retrieve email using EWS + Microsoft OAuth 2.0 in background service - example

Imports System
Imports System.Text
Imports System.IO
Imports System.Net
Imports System.Globalization
Imports EAGetMail

Function _generateFileName(ByVal sequence As Integer) As String
    Dim currentDateTime As DateTime = DateTime.Now
    Return String.Format("{0}-{1:000}-{2:000}.eml",
                    currentDateTime.ToString("yyyyMMddHHmmss", New CultureInfo("en-US")),
                    currentDateTime.Millisecond,
                    sequence)
End Function

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 RetrieveEmail()
    Try
        Dim client_id As String = "b22194da-44d6-4320-a067-e86a275d6fa4"
        Dim client_secret As String = "VTO8Q~eo0JCXc291jcM4wnhZ_GXyKMu."

        ' 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 = "2ea4955d-830e-4aa7-8ab5-661a6b9aa84d"

        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"

        ' Create a folder named "inbox" under current directory
        ' to save the email retrieved.
        Dim localInbox As String = String.Format("{0}\inbox", Directory.GetCurrentDirectory())

        ' If the folder is not existed, create it.
        If Not Directory.Exists(localInbox) Then
            Directory.CreateDirectory(localInbox)
        End If

        ' Office 365 Server address, use access token as password
        Dim oServer As New MailServer("outlook.office365.com",
                officeUser,
                parser.AccessToken,
                ServerProtocol.ExchangeEWS) ' Use Http EWS Protocol

        ' User OAUTH 2.0
        oServer.AuthType = ServerAuthType.AuthXOAUTH2
        ' Enable SSL/TLS connection,
        oServer.SSLConnection = True

        Console.WriteLine("Connecting {0} ...", oServer.Server)

        Dim oClient As New MailClient("TryIt")
        oClient.Connect(oServer)

        ' Get New email only, if you want to get all emails, please remove this line
        oClient.GetMailInfosParam.GetMailInfosOptions = GetMailInfosOptionType.NewOnly

        Dim infos As MailInfo() = oClient.GetMailInfos()
        Console.WriteLine("Total {0} email(s)", infos.Length)

        For i As Integer = 0 To infos.Length - 1
            Dim info As MailInfo = infos(i)
            Console.WriteLine("Index: {0}; Size: {1}; UIDL: {2}",
                info.Index, info.Size, info.UIDL)

            ' Retrieve email from email server
            Dim oMail As Mail = oClient.GetMail(info)

            Console.WriteLine("From: {0}", oMail.From.ToString())
            Console.WriteLine("Subject: {0}" & vbCr & vbLf, oMail.Subject)

            ' Generate an unqiue email file name based on date time.
            Dim fileName As String = _generateFileName(i + 1)
            Dim fullPath As String = String.Format("{0}\{1}", localInbox, fileName)

            ' Save email to local disk
            oMail.SaveAs(fullPath, True)

            ' Mark email as read to prevent retrieving this email again.
            oClient.MarkAsRead(info, True)

            ' If you want to delete current email, please use Delete method instead of MarkAsRead
            ' oClient.Delete(info)

        Next

        ' Quit and expunge emails marked as deleted from  server.
        oClient.Quit()
        Console.WriteLine("Completed!")

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

Register SMTP/POP/IMAP service principals in Exchange

Although the application is consented by the tenant admin, but to access SMTP/POP/IMAP service, the tenant administrator still need to register your application as service principal in Exchange via Exchange Online PowerShell. This is enabled by the New-ServicePrincipal cmdlet.

New-ServicePrincipal -AppId <APPLICATION_ID> -ServiceId <OBJECT_ID>

Find APPLICATION_ID and OBJECT_ID

You should find your APPLICATION_ID and OBJECT_ID before running above cmdlet. Go to Overview -> Managed application in local directory:

Managed application in local directory

After you click your application name in Managed application in l..., you can see Application ID and Object ID for New-ServicePrincipal cmdlet.

find object id in Managed application in local directory

Open Exchange Online PowerShell

Now you need to open Exchange Online PowerShell to run the cmdlet. If you have not installed the module, you can use the Install-Module cmdlet to install the module from the PowerShell Gallery.

Install-Module -Name ExchangeOnlineManagement

After you’ve installed the module, open a PowerShell window and load the module by running the following command:

Import-Module ExchangeOnlineManagement

Connect-ExchangeOnline -UserPrincipalName "admin@yourdomain.onmicrosoft.com"

Create service principal

After Exchange Online PowerShell is connected successfully, run the following cmdlet to create a new service principal: The ServiceId is the OBJECT_ID and the AppId is APPLICATION_ID found in Find APPLICATION_ID and OBJECT_ID

New-ServicePrincipal -AppId "b22194da-44d6-4320-a067-e86a275d6fa4" -ServiceId "71941e67-ef24-45e8-bd22-dfd53790bb77"

Query service principal

After you create the service principal, you can query it by:

Get-ServicePrincipal

Add permission to specific user

You can now add the specific mailboxes in the tenant that will be allowed to be access by your application. This is done with the Add-MailboxPermission cmdlet.

Add-MailboxPermission -Identity <mailboxIdParameter> -User <SecurityPrincipalIdParameter|OBJECT_ID>  -AccessRights <MailboxRights[]>

For example:

Add-MailboxPermission -Identity "grant-test@emailarchitect.net" -User "71941e67-ef24-45e8-bd22-dfd53790bb77" -AccessRights FullAccess

Query permission

You can also query the permission by:

Get-MailboxPermission -Identity "grant-test@emailarchitect.net"

Now you can use IMAP or POP3 protocol to retrieve email by the following codes:

VB.NET/ASP.NET/ASP MVC - Retrieve email using IMAP + Microsoft OAuth 2.0 in background service - example

Imports System
Imports System.Text
Imports System.IO
Imports System.Net
Imports System.Globalization
Imports EAGetMail

Function _generateFileName(ByVal sequence As Integer) As String
    Dim currentDateTime As DateTime = DateTime.Now
    Return String.Format("{0}-{1:000}-{2:000}.eml",
                    currentDateTime.ToString("yyyyMMddHHmmss", New CultureInfo("en-US")),
                    currentDateTime.Millisecond,
                    sequence)
End Function

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 RetrieveEmail()
    Try
        Dim client_id As String = "b22194da-44d6-4320-a067-e86a275d6fa4"
        Dim client_secret As String = "VTO8Q~eo0JCXc291jcM4wnhZ_GXyKMu."

        ' 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 = "2ea4955d-830e-4aa7-8ab5-661a6b9aa84d"

        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 = "grant-test@emailarchitect.net"

        ' Create a folder named "inbox" under current directory
        ' to save the email retrieved.
        Dim localInbox As String = String.Format("{0}\inbox", Directory.GetCurrentDirectory())

        ' If the folder is not existed, create it.
        If Not Directory.Exists(localInbox) Then
            Directory.CreateDirectory(localInbox)
        End If

        ' Office 365 Server address, use access token as password
        Dim oServer As New MailServer("outlook.office365.com",
                officeUser,
                parser.AccessToken,
                ServerProtocol.Imap4) ' Use IMAP Protocol

        ' User OAUTH 2.0
        oServer.AuthType = ServerAuthType.AuthXOAUTH2
        ' Enable SSL/TLS connection,
        oServer.SSLConnection = True
        ' Set IMAP4 SSL Port
        oServer.Port = 993

        Console.WriteLine("Connecting {0} ...", oServer.Server)

        Dim oClient As New MailClient("TryIt")
        oClient.Connect(oServer)

        ' Get New email only, if you want to get all emails, please remove this line
        oClient.GetMailInfosParam.GetMailInfosOptions = GetMailInfosOptionType.NewOnly

        Dim infos As MailInfo() = oClient.GetMailInfos()
        Console.WriteLine("Total {0} email(s)", infos.Length)

        For i As Integer = 0 To infos.Length - 1
            Dim info As MailInfo = infos(i)
            Console.WriteLine("Index: {0}; Size: {1}; UIDL: {2}",
                info.Index, info.Size, info.UIDL)

            ' Retrieve email from email server
            Dim oMail As Mail = oClient.GetMail(info)

            Console.WriteLine("From: {0}", oMail.From.ToString())
            Console.WriteLine("Subject: {0}" & vbCr & vbLf, oMail.Subject)

            ' Generate an unqiue email file name based on date time.
            Dim fileName As String = _generateFileName(i + 1)
            Dim fullPath As String = String.Format("{0}\{1}", localInbox, fileName)

            ' Save email to local disk
            oMail.SaveAs(fullPath, True)

            ' Mark email as read to prevent retrieving this email again.
            oClient.MarkAsRead(info, True)

            ' If you want to delete current email, please use Delete method instead of MarkAsRead
            ' oClient.Delete(info)

        Next

        ' Quit and expunge emails marked as deleted from  server.
        oClient.Quit()
        Console.WriteLine("Completed!")

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

Access token lifetime

You don’t have to request access token every time. By default, access token expiration time is 3600 seconds, you can reuse the access token repeatedly before it is expired.

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.

Appendix

Comments

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

See Also