Category Archives: Exchange

Exchange 2010 hybrid, SMTP, SSL Certificates and Subject Alternative Names

On every Exchange server you need SSL certificates for authentication, validation and encryption purposes. For SMTP you can use the self-signed certificate. Exchange 2010 uses opportunistic TLS, so the self-signed certificate will do in this scenario. If you need to configure domain security (mutual TLS) on Exchange, you need a proper 3rd party SSL certificate for this.

SMTP communication between Office 365 and Exchange in a hybrid scenario is an example of mutual TLS or domain security. A proper 3rd party SSL certificate is needed on your Exchange server.

I was always under the impression that mutual TLS can only use the Common Name of the certificate, which in my scenario is After a previous blogpost there was an interesting discussion (see the comments of this particular blogpost) about this, so now it’s time to do some testing.

Originally I had a Digicert SSL certificate with Common Name, and a Subject Alternative Name entry During the HCW I entered and selected the proper certificate.

It was time to renew my SSL certificate, so I added an additional SAN entry


Continue reading Exchange 2010 hybrid, SMTP, SSL Certificates and Subject Alternative Names

Exchange 2010 Hybrid cannot establish Mutual TLS wrong certificate is used

When configuring an Exchange 2010 hybrid environment a Receive Connector is created on the Exchange 2010 server. This Receive Connector is configured with the FQDN entered in the Hybrid Configuration Wizard (see previous blog post on Exchange 2010 Hybrid) and the source IP addresses of the Microsoft Exchange Online servers. If one of these servers access the Exchange 2010 environment, they end up on the Office 365 Receive Connector (based on the IP address) and the correct SSL certificate is returned. This way mutual TLS is established between Exchange 2010 on-premises and Exchange Online.

It sometimes happens that the wrong certificate is used for SMTP communication between Exchange on-premises and Exchange Online, thus resulting in SMTP mail flow failure between the two.

You can check this in the Exchange Admin Center (EAC) in Exchange Online. Logon to the EAC in Exchange Online, select Mail Flow and click the Connectors tab. You’ll see two connectors. One connector for mail from Exchange 2010 to Exchange Online, and one connector for mail from Exchange Online to Exchange 2010.


Continue reading Exchange 2010 Hybrid cannot establish Mutual TLS wrong certificate is used

Moving from Exchange 2010 to Office 365 Part II

In my previous blogpost, I’ve discussed the prerequisites for moving from Exchange 2010 to Office 365 when using Directory Synchronization (using Azure AD Connect). In this blogpost I’ll discuss how to create an Exchange 2010 hybrid environment.

Exchange 2010 Hybrid

Now that Directory Synchronization is in place using Azure AD Connect we can focus on connecting the on-premises Exchange environment to Exchange Online, this a called an Exchange Hybrid Configuration.

Hybrid configurations can consist of Exchange 2010, Exchange 2013 or Exchange 2016 or a combination of versions, so it is possible to have an Exchange 2010 and Exchange 2013 coexistence scenario on-premises, and connect this to Exchange Online. However, when using multiple versions of Exchange in a Hybrid configuration there’s always add complexity, and when configured incorrectly you can get unexpected results. Therefore, I typically recommend using only one version, so if you’re running Exchange 2010 on-premises, there’s no need to add an Exchange 2013 or Exchange 2016 server to your configuration, just as a ‘hybrid server’. Despite what other people tell you, there’s no need to add a newer version, and Exchange 2010 Hybrid is fully supported by Microsoft. Better is to create an Exchange 2010 hybrid environment, and when the mailboxes (or most the mailboxes) are moved to Office 365 upgrade your existing Exchange 2010 environment to Exchange 2016. But that might be an interesting topic for a future blog post Smile.

Basically, we will create the following configuration (again, there is no Exchange 2016 server installed in the existing organization):


Figure 14. Exchange 2010 hybrid configuration.

Continue reading Moving from Exchange 2010 to Office 365 Part II

Moving from Exchange 2010 to Office 365

There are a lot of articles on the Internet on how to create a hybrid environment, where Exchange 2016 is connected to Office 365. Now that’s fine, but when you’re running Exchange 2016 you most like are NOT going to move to Office 365 anytime soon I guess. If you are running Exchange 2010 chances are that you will move to Office 365 (soon), but there aren’t that much articles about moving from Exchange 2010 to Office 365. And a lot of the articles available don’t have the right approach I’m afraid, and will result in you (the customer) having to pay way too much money to your system integrator.

In this article, I’ll try to outline the recommended approach when moving from Exchange 2010 to Office 365 in a hybrid scenario. With Azure AD Connect for synchronization purposes. Cliffhanger: I’m not going to install Exchange 2016 into the existing Exchange 2010 environment Smile

Existing Exchange environment

Our organization is called Inframan and they have their own on-premises Exchange 2010 environment which they have been running for 5 years now without too much issues. There are internal Outlook clients using Outlook 2010 and higher, and there are external clients using Outlook Anywhere. There are also mobile clients using ActiveSync to connect to their Mailboxes. Of course, there is Outlook Web Access, but POP3 and IMAP4 are not used.


Figure 1. Overview of the Inframan Exchange 2010 environment.

Continue reading Moving from Exchange 2010 to Office 365

I’m speaking at IT/Dev Connections 2017

The IT/Dev Connections 2017 takes place in San Francisco from October 23-26. IT/Dev Connections is a highly technical and non blahblah event, delivered by professionals for professionals. To give you an idea, this is the only event (I think) that has no keynote sessions, just a small talk 5 minutes before the welcome drink on the first day of the event.

There are five technical tracks:

  • Cloud and Datacenter.
  • Data platform & business intelligence.
  • Enterprise Collaboration.
  • Enterprise Management, Mobility and Security.
  • Development and DEVOPS.

I’ve submitted a couple of sessions (surprisingly in the Enterprise Collaboration track) and I’m happy to announce two sessions were selected:

  • High Availability in a Microsoft federated infrastructure –
    October 25, 9:15 AM
  • Message Security – Is this legitimate email or not? –
    October 26, 8:30 AM

If you’d like to join me and other already confirmed speakers like Bert Wolters and Sander Berkouwer, use the following link to register!

The last 15 editions the event took place in Las Vegas, this is the first time it is NOT in Las Vegas but in San Francisco, in the Hilton San Francisco Union Square.

Want to know more? Any ideas or feedback? Just leave a comment below or drop me an email. I’m looking forward to see you all again in San Francisco!