gscales

NetworkCredential networkCredential = new NetworkCredential("blah@blah.onmicrosoft.com", "blah");
PublicClientApplicationBuilder pcaConfig = PublicClientApplicationBuilder.Create("d64799fe-dfb2-480b-a3be-a7a5a0bdaf32").WithTenantId("eb8db77e-65e0-4fc3-b967-b14d5057375b");
var app = pcaConfig.Build();
var tokenResult = app.AcquireTokenByUsernamePassword(new string[] { "https://outlook.office.com/POP.AccessAsUser.All" }, networkCredential.UserName, networkCredential.SecurePassword).ExecuteAsync().GetAwaiter().GetResult();
var saslformatedToken = Convert.ToBase64String(ASCIIEncoding.ASCII.GetBytes("user=" + networkCredential.UserName + (char)1 + "auth=Bearer " + tokenResult.AccessToken + (char)1 + (char)1));
var client = new Pop3Client();
client.Connect("outlook.office365.com", 995, true);
client.Authenticate(networkCredential.UserName, saslformatedToken, AuthenticationMethod.XOAUTH2);
int messageCount = client.GetMessageCount();
var lastMessage = client.GetMessage(messageCount);            

gscales

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Microsoft.Exchange.WebServices.Data;
using System.Threading.Tasks;
using System.Net;
using System.Security;
using Microsoft.Identity.Client;
using System.Net.Http;

gscales

  Create a Draft message
  
  POST https://graph.microsoft.com/v1.0/users('gscales@.....com')/mailfolders/drafts/messages HTTP/1.1
  
  {
  "Subject": "Test Message 1234",
  "Body": {
    "ContentType": "HTML",
    "Content": "Rgds Glen"
  },

gscales

using System;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Net.Http;
using System.Net.Http.Headers;
using Microsoft.Identity.Client;
using Newtonsoft.Json;
using Microsoft.Graph;
using System.IO;

gscales

function Get-AccessTokenForGraphFromCertificate{
    param(
        [Parameter(Position = 1, Mandatory = $true)]
        [String]
        $TenantDomain,
        [Parameter(Position = 2, Mandatory = $true)]
        [String]
        $ClientId,
		[Parameter(Position = 3, Mandatory = $false)]
		[System.Security.Cryptography.X509Certificates.X509Certificate2]

gscales

<soap:Envelope
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xmlns:m="http://schemas.microsoft.com/exchange/services/2006/messages"
	xmlns:t="http://schemas.microsoft.com/exchange/services/2006/types"
	xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
	<soap:Header>
		<t:RequestServerVersion Version="Exchange2016" />
	</soap:Header>
	<soap:Body>
		<m:FindItem Traversal="Shallow">

gscales

Extended property Definition for isExternalSender

$isExternalSender = new-object Microsoft.Exchange.WebServices.Data.ExtendedPropertyDefinition([Guid]::Parse("41F28F13-83F4-4114-A584-EEDB5A6B0BFF"),"IsExternalSender", [Microsoft.Exchange.WebServices.Data.MapiPropertyType]::Boolean) 

Using it in FindItems

$ItemPropset = new-object Microsoft.Exchange.WebServices.Data.PropertySet([Microsoft.Exchange.WebServices.Data.BasePropertySet]::FirstClassProperties)
$ItemPropset.Add($isExternalSender)
$ivItemView = New-Object Microsoft.Exchange.WebServices.Data.ItemView(1000) 
$ivItemView.PropertySet = $ItemPropset

gscales

Include the IsExternalSender property in Results 

https://graph.microsoft.com/v1.0/users('user@dom.com')/MailFolders('Inbox')/messages/?
$Top=10&$expand=SingleValueExtendedProperties($filter=(Id eq 'Boolean {41F28F13-83F4-4114-A584-EEDB5A6B0BFF} Name IsExternalSender'))

Filter for only External Senders

https://graph.microsoft.com/v1.0/users('user@dom.com')/MailFolders('Inbox')/messages/?
$Top=10&$filter=singleValueExtendedProperties/Any(ep:+ep/id+eq+'Boolean+{41F28F13-83F4-4114-A584-EEDB5A6B0BFF}+Name+IsExternalSender'+and+cast(ep/value,+Edm.Boolean)+eq+true)&$expand=SingleValueExtendedProperties($filter=(Id eq 'Boolean {41F28F13-83F4-4114-A584-EEDB5A6B0BFF} Name IsExternalSender'))

gscales

    function FindFolderRequest(){
        var RequestString =
        '<?xml version="1.0" encoding="utf-8"?>' +
        '<soap:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:m="http://schemas.microsoft.com/exchange/services/2006/messages" xmlns:t="http://schemas.microsoft.com/exchange/services/2006/types" xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">' +
        '  <soap:Header>' +
        '    <t:RequestServerVersion Version="Exchange2016" />' +
        '  </soap:Header>' +
        '  <soap:Body>' +
        '<m:FindFolder Traversal="Shallow">' +
        '<m:FolderShape>' +

gscales

$folderid= new-object Microsoft.Exchange.WebServices.Data.FolderId([Microsoft.Exchange.WebServices.Data.WellKnownFolderName]::Inbox,$MailboxName)   
$TeamsMessagesDataFolderEntryId = new-object Microsoft.Exchange.WebServices.Data.ExtendedPropertyDefinition([System.Guid]::Parse("{E49D64DA-9F3B-41AC-9684-C6E01F30CDFA}"), "TeamsMessagesDataFolderEntryId", [Microsoft.Exchange.WebServices.Data.MapiPropertyType]::Binary);
$psPropset= new-object Microsoft.Exchange.WebServices.Data.PropertySet([Microsoft.Exchange.WebServices.Data.BasePropertySet]::FirstClassProperties) 
$psPropset.Add($TeamsMessagesDataFolderEntryId)
$RootFolder = [Microsoft.Exchange.WebServices.Data.Folder]::Bind($service,$folderid,$psPropset)        
if ($RootFolder.TryGetProperty($TeamsMessagesDataFolderEntryId,[ref]$FolderIdVal))
{
     $TeamsMessagesFolderId= new-object Microsoft.Exchange.WebServices.Data.FolderId((ConvertId -HexId ([System.BitConverter]::ToString($FolderIdVal).Replace("-","")) -service $service))
     $TeamsMessagesDataFolder =