Category: Microsoft Exchange

How To: Authenticated SMTP When Security Defaults/Modern Authentication Are Enabled

Background

Many legacy applications use authenticated SMTP to send email notifications. Since most organizations use Exchange Online as their email provider, leveraging it as a mail relay for service accounts is helpful and convenient. About five or so years ago, Microsoft began enabling Security Defaults for all new tenants and, shortly after, began deprecating Basic Authentication in Exchange.

While it’s possible to utilize smtp.office365.com as a relay for appliances such as printers and scanners, this may or may not be feasible in a particular use case, as was my situation. After many hours of research, trial, and error, I’d finally worked through all the pieces to get authenticated SMTP working with Security Defaults and Modern Authentication enabled.

Prerequisites

You’ll need to ensure the following is configured for the account you want to use:

  • MFA is enabled for the target user account in the Microsoft Entra admin center
  • The SmtpClientAuthenticationDisabled property (Exchange Online PowerShell) is set to $false (meaning that authenticated SMTP is enabled for this user)
  • Generate and record an App Password for the user
  • Disable POP3 and IMAP to prevent TLS downgrade attacks (optional, but highly recommended)

Putting it All Together

Instead of targeting smtp.office365.com on port 587 as our mail relay, we’ll use [YourTenantID].protection.outlook.com on port 25 with the StartTLS property (required).

We can use PowerShell to test this:

Send-MailMessage -SmtpServer [YourTenantID].protection.outlook.com -UseSsl -Port 25 -From me@mydomain.com -To you@yourdomain.com -Subject "Test Email" -Body "Testing, 1, 2, 3?"

Yes, I know the Sent-MailMessage cmdlet is obsolete and doesn’t guarantee secure connections to SMTP servers, but in this case, we’re only using it to test our settings and connectivity.

If it works, we know that any remaining fault lies with the application configuration and/or the environment it resides in, not your Microsoft 365 setup.

Targeted Email Removal with Exchange Online Powershell

In the course of administering an Exchange Online instance I’m occasionally asked to locate and remove an email (or set of emails) from the entire tenant. The quickest way to do this is via PowerShell:

Connect to the Exchange Online instance, enter your credentials when prompted:

Connect-ExchangeOnline

Next, Connect to the Security and Compliance Center PowerShell, entering your credentials again when prompted:

Connect-IPPSSession

Now that you’re connected, you can create a new compliance search to locate the email(s) you wish to remove:

New-ComplianceSearch [SearchName] -ExchangeLocation 'All' -ContentMatchQuery 'from: "*@something.com"'

In the example above, I’m searching for all content across all mailboxes from a specific domain (e.g. @something.com), but you can modify the scope of the search by adjusting the location and content match query (i.e. searching by subject or just looking at specific mailboxes/folders etc.).

Once the search is created, you will need to start it:

Start-ComplianceSearch [SearchName]

While the search is ongoing, you can check on its status:

Get-ComplianceSearch [SearchName]

NOTE: You can use the “|fl“ parameter to obtain additional information on the compliance search status.

Once completed, you can use the purge the emails located by the search:

New-ComplianceSearchAction -SearchName [SearchName] -Purge -PurgeType SoftDelete

 

Email Hide and Go Seek: How to locate a specific email (down to the folder) in Office 365 using PowerShell

In many organizations, end users receive too much email to manage effectively. Many utilize rules to filter emails into specific buckets to make them easier to find. Over time, these rules compound, and could eventually lead to unintended consequences (i.e. receiving an email but being unable to find it).

When this happens, I’d typically run a quick message trace to establish whether the email was actually delivered or not. Many admins will stop there, advising the end-user to check their rule settings, but using PowerShell, we can find the email(s) for them!

First, let’s get logged into the Office 365 tenant:

$Credential = Get-Credential
$ExchangeSession = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri "https://outlook.office365.com/powershell-liveid" -Credential $credential -Authentication "Basic" -AllowRedirection
Import-PSSession $ExchangeSession

Next, we can determine how many emails match the criteria in case there are more than one (Optional):

search-mailbox -EstimateResultOnly -identity [target user] -searchquery 'from:"[sender emai]" AND subject:"subject"'

Now for the coup de grâce, to reconstruct precisely which folder and sub-folder(s) of where the email(s) that match that criteria are in the user’s inbox:

search-mailbox -identity [recipient] -searchquery 'from:"[sender]" AND subject:"[subject] "' -targetmailbox "[your email] " -targetfolder "SearchResults"

In your inbox, you’ll see a folder called ‘SearchResults’. Using this, you can guide the end-user through the folder structure on their own Inbox that they’ll need to traverse to get to the desired email(s).