Tag Archives: hybrid

Exchange 2010 and TLS 1.2

In a previous blogpost I discussed an issue I had with Outlook 2010 and TLS 1.2. At the same time this reminded me that Microsoft will remove support for TLS 1.0 and TLS 1.1 in Office 365 on October 31, 2018 as communicated in https://support.microsoft.com/en-us/help/4057306/preparing-for-tls-1-2-in-office-365. This means that when you have communication issues with Office 365 because of an older and weaker protocol, you won’t get any support. Time to do some research….

Existing Exchange 2010 environment

As you may have seen on this side, I still am a big fan of Exchange 2010 and also have an pure Exchange 2010 hybrid environment up-and-running and it looks like this:

Inframan-hybrid

MX records is pointing to my Exchange 2010 Edge Transport Server (running on Windows 2008 R2), webmail and Autodiscover are routed via an F5 LTM load balancer to an Exchange 2010 CAS/HUB/Mailbox server (also running on Windows 2008 R2), and hybrid is configured directly on Exchange 2010 (for hybrid mail flow I’m using a separate FQDN, o365mail.inframan.nl) without any Exchange 2013 or Exchange 2016 server.

So, how do you test which TLS version is used by your Exchange 2010 server? In Exchange 2010 this should be done using the protocol logfiles. Message headers in Exchange 2010 do not contain enough information for showing this TLS information. So, you must enable protocol logging for the appropriate Receive Connectors and Send Connectors. In my environment this means the Default Receive Connector on the Exchange 2010 Edge Transport server (for O365 traffic from other tenants), the Default-First-Site-Name to Internet Send Connector, and both connectors between the Exchange 2010 server and Office 365 for hybrid. Analyzing the protocol logfiles can best be done in Excel (import as CSV files). When analyzing, look for a string like TLS protocol SP_PROT_TLS1_0_SERVER (when receiving) or TLS protocol SP_PROT-TLS1_0_CLIENT (when sending). When TLS 1.2 is used, look for a string like TLS protocol SP_PROT_TLS1_2_SERVER and TLS protocol SP_PROT-TLS1_2_CLIENT.

Continue reading Exchange 2010 and TLS 1.2

Cannot find a recipient that has mailbox GUID when moving from Exchange Online to Exchange 2016

When moving mailboxes from Exchange Online to Exchange 2016 on-premises in a hybrid environment, the move fails with an error “Cannot find a recipient that has mailbox GUID ‘ ‘

image

The error is listed here for Search Engine purposes:

Error: MigrationPermanentException: Cannot find a recipient that has mailbox GUID ‎’add02766-9698-48e6-9234-91c3077137bc’. –> Cannot find a recipient that has mailbox GUID ‎ add02766-9698-48e6-9234-91c3077137bc ‎’.
Report: bramwess@exchangelabs.nl

When checking the user account with ADSI Edit in the on-premises Active Directory it is obvious that this property is empty:

image

When checking the Mailbox in Exchange Online (using Remote PowerShell) the Exchange GUID is visible when using the command

Get-Mailbox -Identity name@exchangelabs.nl | Select Name,*GUID*

As shown in the following screenshot:

image

It took me some time to figure out why this property was empty. Normally when moving mailboxes from Exchange on-premises to Exchange Online the Mailbox GUID is retained. Keeping the Mailbox GUID makes sure you don’t have to download the .OST file again after moving to Exchange Online.

What happened here is that the user was created in Active Directory on-premises, and a Mailbox was directly created in Exchange Online using the Enable-RemoteMailbox command. In this scenario, there never was a Mailbox on-premises and thus never a Mailbox GUID.

The solution is to copy and paste the Mailbox Guid as found in the previous command into the Remote Mailbox object on-premises using the Set-RemoteMailbox command

Set-RemoteMailbox user@exchangelabs.nl -ExchangeGuid “copied value”

As shown in the following screenshot:

image

When setting the Mailbox Guid the mailbox can be moved from Exchange Online to Exchange on-premises.

Ps. Don’t forget to repeat this for anchive mailbox (if one exists)

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 CN=webmail.inframan.nl. 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 CN=webmail.inframan.nl, and a Subject Alternative Name entry autodiscover.webmail.com. During the HCW I entered webmail.inframan.nl and selected the proper certificate.

It was time to renew my SSL certificate, so I added an additional SAN entry o365mail.inframan.nl.

image

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.

image

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

Change SMTP mail flow in hybrid scenario

After building a hybrid Exchange environment as outlined in a couple of previous blog posts we have an Exchange 2013/2016 environment where some Mailboxes exist on-premises and some Mailboxes exist in Exchange Online. Autodiscover is still pointing to the on-premises environment, and so are the MX records. Inbound SMTP mail flow from the Internet is still accessing the on-premises Exchange 2016 Edge Transport servers before being delivered to the intended recipients.

image

Figure 1. The Exchange hybrid environment with Mailboxes on-premises and in Exchange online.

Continue reading Change SMTP mail flow in hybrid scenario