Creating, Sharing, & Searching a Singular Outlook Calendar from multiple emails w/ different domains

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I am hoping this amazing community of tech-savvy, smart, resourceful people can help me come up with a solution to my Outlook calendar problem. I work for a family of companies where employees have multiple email addresses with different domains. For example, I currently have (4) four email addresses associated with my Outlook account. (1) One email is my user account associated with my O365 license and the other (3) three are set up as shared inboxes that are shared with only me. Each of those (3) emails is under a different domain and has full access through mailbox delegation. Each email has its own calendar in my Outlook exchange profile. I would like to only have one calendar associated with my person to make using O365 features such as scheduling assistant and shared calendar useful. Does anyone have suggestions for how to achieve this? 

Does anyone else have a similar issue or know of a workaround/solution?


Thus far I've tried:

1) Dragging and Dropping the items onto my main calendar, but this is not feasible to maintain and it still doesn't fully solve the issue of others within the family of companies searching my calendar because they will still find four. 

2) Creating a group with the calendars via the Outlook Desktop app, that others in my company could then search the group and use to view my schedule and also send invites to the group to schedule a time with me. 
When doing this via the Outlook Desktop app, I was able to create a group that allowed me to view all (4) four calendars on one screen but the information was still on (4) four different calendars. Also, the group was not searchable or shareable. Following Microsoft support instructions, I then tried to merge the information from the calendars onto one. This worked but it created (4) new calendars that had all the items on them. 
**This could potentially work if there was a way to make it so that the calendars didn't have to be manually merged every day and (4) new calendars weren't created every day. And there was also some way to stop items from duplicating. **

3) Creating a group with the calendars via Outlook Online (Web), that others in my company could then search the group and use to view my schedule and also send invites to the group to schedule a time with me. 
When doing the via Outlook Online (Web) I was able to create a new group (which created a new email for the group as well) and share it, but others could not search the group to view the calendar or use the scheduling assistant. 


4) Creating a rule that forwards all calendar invites to my main email address. I was able to set up this rule via the Outlook Desktop App. However the rule did not work on the test calendar invites I had some coworkers send me, but it did work on some old Teams meeting updates I had received. **Does anyone know if there is a certain way the invites have to be sent for the rule to work?**
I attempted to set the rule op via Outlook Online (Web) but could not find this rule option. 


5) I also looked in the Calendar conditional formatting, but could not find any options for moving items just highlighting them different colors. 

Currently trying:

I am currently looking into the option of using Power Automate to achieve this. If anyone has any ideas on how that might work as well. 

To recap:
I want one calendar associated with my person that links with all my email addresses regardless of the domain and shared inbox status. Ideally, people could send an invite to any email address and it would all go to one calendar, and when people look me up to invite me to something they would only have to add my one calendar and it would contain all events. 

Thank you in advance for any guidance provided!

4 Replies
So are all those domains in the same Office 365 tenancy, or separate ones? If the former, you can ask your IT folks to add all the addresses as aliases to your mailbox, thus removing the need to handle multiple other mailboxes.
Hi Vasil, they are the same tenancy. The problem is that all the mailboxes have their own calendar. Would doing as you suggest merge all of the calendars?
It will not merge them (as in any existing items will not be copied), but going forward you can use a single calendar for all addresses.
I have the same issue (Multiple calendars) but with different tenancy and domains. Any clue on how to resolve this?