Hide User from GAL - Office 365 | AD Attribute

The following method will allow you to hide a user from the Global Address List if you're using Office 365 with Azure AD Connect.

From within AD, click on View, then Advanced Features

Find the user you'd like to amend and open up their AD object (note you will need to find the user account within AD, you can't search for it).

Find the following attribute and set it to True

msExchHideFromAddressLists

The next time Azure AD Connect syncs, it will update this attribute and the users will be hidden from the GAL.

Note: the GAL can take up to 24 hours to sync for each Outlook application.

Update Hyper-V Integration Services

I was recently on a Hyper-V host where a few of the VMs were saying the integration services required an update.

To update this, open up the VM through Hyper V manager, then click Action > Insert Integration Services Setup Disk.

Run the setup from within the VM

A message will show up saying that it's detected a previous version of the services and asks whether you'd like to upgrade it

Once you've clicked OK, it will give you a progress bar for the installation

Once finished installing, you will need to restart the VM

The final step is to simply eject the Integration Services from the VM

This process will need to be carried out on each VM you're running in your environment, if you notice it requires an Integration Services update.  Just note that because of the reboot, it will cause down-time. 

Office 365 Hybrid Deployment - Mail Loop

If you're ever in the middle of an Office 365 Hybrid deployment, you've configured everything correctly but you notice that when you're testing the mail flow from one premise to the other, it's causing a continuous mail flow (you will receive a NDR), the first thing I would suggest you look into is whether there's a gateway in the middle of your on-prem Exchange and your Office 365 environment.

Office 365 Hybrid is only supported if you have nothing between your on prem Exchange, and the O365 environment.  That means no IronPorts etc getting in the way.

I recently encountered an issue where there was a continuous mail flow symptom.  Office 365 was trying to deliver the email to on prem Exchange, it was caught up in the IronPort and then it tried to deliver it back to Office 365.  To get around this I opened Exchange up to the internet by NATting Port 25 on a different WAN IP which would bypass the IronPorts entirely.  I amended the Connectors in Office 365 so they'd connect through that address, rather than through the IronPorts.

Once this was done, the issue resolved itself immediately.