Outlook will release weekly updates to production beginning March 21, 2023
Page Last Updated: March 20, 2023 @ 1:00pm Pacific Time


On February 16, 2023 Microsoft posted MC516354 to the Microsoft 365 Message Center saying that Outlook for Mac will soon release updates on a weekly basis.
This document delves a little deeper into the upcoming change and answers questions that Mac IT admins may have about how this may affect them.

NOTE: To access the Message Center, you must be logged in to Microsoft 365 with an account that has the appropriate permissions.

Rude Q&A

1. Tell me again, what is this change, and how does it compare to what Microsoft has been doing previously?
Since mid-2015, Office for Mac updates have been released to production on a monthly basis. These updates usually include security fixes, new features, and performance and reliability fixes (aka bug fixes).
Starting on 3/21/23, with Outlook for Mac specifically, updates will be published to production on a weekly basis.

2. Why does Microsoft want to change Outlook releases to weekly?
For the last few years, Outlook has gone through some major changes - everything from swapping the core sync protocol from EWS to Hx - to re-writing he user interface.
However, users continue to demand more functionality but the current release cadence doesn't lend itself well to providing constant innovation, and bringing major new enhancements to users.
Features that are planned for a monthly update can run into a simple last minute problem, which results in a minimum 4-6 week delay. This causes frustration for customers who had planned to utilize the new feature immediately.
Shipping updates on a weekly basis goes a long way to solve these problems.

3. Wait, if you ran into a last minute problem leading up to a monthly update isn't it a good thing to pause and make sure everything is re-tested and properly working for the next release?
That argument does make sense from a quality perspective. Neither Microsoft nor customers want updates that are unreliable and not ready for the prime-time.
However, modern apps use a variety of methods to dynamically adjust the exposure of code paths that say, make a feature light-up, or cause certain logic to be executed.
Put another way, the actual build of the app installed on a device is just the starting point of a user's product experience.
Like many other apps, Outlook constantly checks-in with a back-end service at Microsoft to get instructions on what code-paths it should be executing, and how to provide the best experience.
This is similar to how the pilot of an airplane has a well-thought out flight plan for how to reach a destination, but keeps in constant check with the tower to make fine adjustments to the route.
In the same way that the tower tells the pilot to move to lower altitude to avoid unexpected turbulence, the Microsoft 'tower' can tell Outlook clients to avoid a certain code-path that's causing problems. All this is possible without needing a client-side update.

4. Does this mean that security updates will also be delivered in those weekly Outlook updates?
No. Any security updates pertaining to Outlook will be only delivered in the Outlook update that aligns with the monthly Suite release (commonly known as 'Patch Tuesday').
Put another way, security updates will still be on a monthly cadence.

5. Are the other apps in the suite like Word, Excel, and PowerPoint going to move to a weekly cadence as well?
No, not at this time. These apps will remain on their monthly cadence for the foreseeable future.

6. What does this mean for the Office Suite installer - will this also be updated and released weekly?
No. The Suite installer will continue to be released on its existing monthly cadence, and will include the build of Outlook that aligns with Patch Tuesday.

7. What does the versioning look like in this new world?
The monthly (or Patch Tuesday) release of Outlook will end with .0 as it does today (e.g. 16.71.0). On the following Tuesday, Outlook will be released with a .1 suffix (e.g. 16.71.1)
This will continue with .2, .3, .4, etc.

8. So, these weekly Outlook releases will occur on Tuesdays?
Yes, this should be your expectation. A 'release candidate' build will be published to the Preview channel on Mondays, and if all looks good, that same build will be promoted to the Current channel the following day.
It's possible that there are no fixes or updates for certain weeks, in which case, there will be no update.
It's also possible that unexpected build or infrastructure issues cause a 24-hour slip in the release (i.e. in rare cases you could see the update on Wednesday instead of the expected Tuesday).
If the slip is going to be more than 24-hours, the update for that week will be abandoned

9. What about the Mac AppStore - will that get weekly Outlook updates?
Yes. The weekly Outlook updates will be published to both the Mac AppStore and Office CDN.
When using the Mac AppStore or VPP-based distribution, only the latest weekly update of Outlook will be available.
If you are using the CDN, all updates are available - both weekly and monthly, including all previous releases of weekly and monthly updates.

10. If I'm using Microsoft AutoUpdate and my users are on the Current Channel, what will their experience be with weekly Outlook updates?
Every Tuesday, Microsoft AutoUpdate will automatically detect and download the weekly update in the background. The What's New 'megaphone' icon in the top right of the Outlook title bar will show a red indicator.
Clicking the What's New icon will reveal the following message:


If the user clicks 'Restart Now' Outlook will quit and restart. The total amount of downtime should be between 10 and 30 seconds.
If the user chooses to ignore the prompt, the existing/older version of Outlook will continue to function, with the new version waiting in the background until Outlook is closed at some future point in time.

11. I'm currently using the deferred and version-pinned channels in MAU. Will these get weekly Outlook updates?
No. Given the intent and nature of these channels, only the monthly Outlook release will be published to these channels.
As is the case today, if a critical hotfix is required for Outlook, that update WILL be published to the deferred and version-pinned channels.

12. I'm a little worried about the size of these weekly updates and the impact that it's going to have on my network. Can you comment?
Yes, the download size of a weekly update is going to depend on how you've designed your update process.

NOTE: The size difference between MAU and MAS are based purely on implementation. MAU uses a binary-delta mechanism which patches changed files based on the binary difference between the old and new versions. For MAS, the update contains complete copies of the changed files, so the resulting update package is larger.

13. Given a build number such as 16.71.1, how will I be able to tell if that refers to a hotfixed version of the monthly Outlook update, or a weekly update?
This can be a little tricky. First up, know that there is only one instance of any given version. That is, if you know that you want to install 16.71.1 there is only one package to download.
The question then becomes, do I need to install 16.71.1? To help with the differentiation, there will be four FWLinks (aka permalinks) to download Outlook. NOTE: An 'installer' package contains a full copy of the app such as Outlook, Microsoft AutoUpdate, and the computer-wide licensing helper (which is used for non-Subscription activation).
An 'update' package contains a full copy of the app, but nothing more.