Classic Outlook not honoring primary calendar when overlayed with shared calendars

Question

Classic Outlook not honoring primary calendar when overlayed with shared calendars

Cody Hinson 5

I have a single outlook account. I have added a shared calendar and overlayed it with my primary calendar. My issue is no matter what I try, every time I close and launch outlook, the shared calendar defaults to the top (active) layer of the calendar overlay instead of my primary calendar.
I have tried resetting my entire office suite, updating Microsoft 365, disabling shared calendar improvements, re-ordering the calendars in the left pane, etc.

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Answer 1

Jayden-P 4,145 Independent Advisor

Hi @Cody Hinson

At first, I was able to reproduce the same behavior in Classic Outlook using the latest Monthly Enterprise Channel version available in my test environment. When a shared calendar is overlaid with the primary calendar, the shared calendar becomes the active overlay layer again after Outlook is closed and reopened.

However, after I drag the primary calendar to the top on the left panel, the default calendar when I start Outlook again is the one on top of the list.

May I ask what is your Classic Outlook version? You can check this in File > Office Account > About Outlook.

Which view are you using? (day/week/work week/month)

You can try rebuild .ost file: Close Outlook > Press Windows + R > Type in %LOCALAPPDATA%\Microsoft\Outlook\ > Look for your email address and delete it > Restart Outlook.

After restart, make sure to drag your primary calendar on top of the list and the shared calendar next.

Jayden is my primary and Lee Gu is shared calendar. And make sure to click on the Calendar tab, if it is in bold, it is the default.

User's image

Please try and let me know how it goes.

Cody Hinson 5 Reputation points

2026-08-27T16:29:32.9666667+00:00

I am using month view and using this version of classic outlook:
Microsoft® Outlook® for Microsoft 365 MSO (Version 2608 Build 16.0.20326.20072) 64-bit

I tried rebuilding the .ost file per your steps and it worked on the initial launch of Outlook. But when I closed and re-launched again it reverted back to the undesired behavior.
Cody Hinson 5 Reputation points

2026-08-27T16:41:33.4866667+00:00

There are actually 2 shared calendars that I've overlayed with primary calendar, and it seems like whichever shared calendar completes its sync last upon first launch is the one that gets displayed on top. When I first open the calendar tab, my personal calendar is the active calendar, but after a second or two the shared calendars complete their sync and then one of them become the active calendar.
Jayden-P 4,145 Reputation points Independent Advisor

2026-08-27T17:04:37.7966667+00:00

Hi,

Thank you for the additional information and for testing after rebuilding the OST.

I attempted to reproduce the behavior in my test environment using two shared calendars overlaid with my primary calendar. However, I was not able to reproduce the same result.

In my testing, after arranging the calendars so that my primary calendar was at the top of the calendar list, it remained the active (bold) calendar even after closing and reopening Outlook.

Based on your description, it differs from my test results, which suggests there may be another factor affecting the behavior in your environment. It could be due to we use different Outlook version. You are using Current channel (Preview), while I'm using Monthly Channel.

As a workaround, you can manually click on the calendar name to make it active.
Jayden-P 4,145 Reputation points Independent Advisor

2026-08-28T16:00:24.2233333+00:00

Hi @Cody Hinson

Any update from you?
Andreas Hoefler 0 Reputation points

2026-11-02T11:45:11.97+00:00

@Jayden-P I experience the exact same behavior as @Cody Hinson has. I have a bunch of local calendars ("My Calendar", "Private", "Holidays") and a shared one (company-related mailbox).

Whenever I (re-)activate the calendar view in Outlook ("Microsoft® Outlook® für Microsoft 365 MSO (Version 2609 Build 16.0.20430.20032) 64 Bit" the overlay of the shared calendar is activated.

I tried the things resetting Outlook caches, disconnecting/reconnecting to the shared mailbox, reordering the mailboxes in the left tab, but to no avail.

The workaround of "manually click on the calendar name" is of course working, but this is still a very annoying (and to a certain extend data-security related) misbehavior.

Update: I just found that there was already a similar issue reported in 2019, here, but as far as I can see there has been no definitive solution also at that time.