How and why should I protect my Office 365 organization from Email Address Internationalization (EAI) attacks?

On 27 December 2017 Microsoft announced that the support for EAI in email has been implemented. This means that the Microsoft cloud now supports EAI email addresses in outlook, email flow, connectors and rules. For now there won’t be any support for adding IDN domains to the platform itself. With this new functionality in Office 365 a new door opens…

Exchange: The security principal specified is already on the permission set

Every once in a while you will find customers running in to the following issue. When they try to get mailbox folder permissions or set mailbox folder permissions  a red error message pops up stating: The security principal specified is already on the permission set. + CategoryInfo          : NotSpecified: (:) [Get-MailboxFolderPermission], CorruptDataException + FullyQualifiedErrorId : [Server=SU8000006141,RequestId=628b5335-6148-4297-8f06-4c607b029737,TimeStamp=15-2-2017 06:46:24] [FailureCategory=Cmdlet-CorruptDataException] BE7556A,Microsoft.Exchange.Management.StoreTasks.GetMailboxFolderPermission + PSComputerName       …

Antispam counter measures explained Part 2: Advanced SPF records,  Best practice and biggest mistakes

Antispam counter measures explained Part 1: How the Sender Policy Framework really works Antispam counter measures explained Part 2: Advanced SPF records,  Best practice and biggest mistakes Antispam counter measures explained Part 3: How DKIM really works and best practice   In Part 1 I explained the basics of SPF and how you can implement the most common scenario`s. After the…

Antispam counter measures explained Part 1: How the Sender Policy Framework really works

Antispam counter measures explained Part 1: How the Sender Policy Framework really works Antispam counter measures explained Part 2: Advanced SPF records, Best practice and biggest mistakes Antispam counter measures explained Part 3: How DKIM really works and best practice   In this first part of “Antispam counter measures explained ” I will start with a detailed explanation of how…

PS Script: Connect to one or multiple Exchange server PowerShell sessions from any computer.

In my previous posts I showed some functions for finding an AD DC and run LDAP query’s against those DC`s. The following function “Connect-Exchangeservice” builds on top of the Get-LDAPobject function. This new function will connect you to the PowerShell management session of an exchange server. This way you do not have to install the exchange management tools to manage exchange via PowerShell. The big…