Merge shared mailbox calendar with main user account calendar in Office 365

Question

Recently I had a problem with some users of a department regarding their email accounts.

This particular department has its own domain within the company, so, these users had their main account for the company (p.ex. ******@company.com) and their department domain email account (p.ex. ******@dep-companion.com). Since they worked more often with their department accounts they have their calendars organized there as well. Recent changes in the company forced a policy to use only the company email accounts. IT department converted all the department accounts to shared mailboxes and each user has delegation rights over them. But since they always worked with the other accounts they receive invitations on their department accounts calendar and say that they can't accept the invitations because the main account is the other one. I know this might seem confusing, I'm sorry if I'm not being clear, but I want to help them and I don't know how to merge the shared calendar with the main one to overcome this issue. I'm not mentioning overlay. Maybe export the calendar? Is there any way to automate this in Office 365 Admin? Please help. Thank you.

Answer 1

Do you have forwarding configured on the other account so that new invites get delivered to their "main" mailbox? Or maybe a mail flow rule to add their main mailbox as additional recipient on any invite/message addressed to the other account?

You can copy the calendar items between the two accounts, either manually or via some EWS-based script, but that won't help with new invites. Is merging both mailboxes not an option? Or removing the email aliases and assigning them to the "main" mailbox?

Alternatively, you can configure the shared mailbox as additional account in Outlook (as opposed to have it added as additional mailbox or automapped), which will allows them to work with those items directly, just like they do with their own calendar items.

Answer 2

Hi @Miguel Correia ，

IT department converted all the department accounts to shared mailboxes and each user has delegation rights over them. But since they always worked with the other accounts they receive invitations on their department accounts calendar and say that they can't accept the invitations because the main account is the other one.

Converting to shared mailboxes and granting the necessary delegation rights to the user is a common practice in this scenario. And based on my experience and test, normally this can work fine enough.

If the old email address "@dep-companion.com" is intended to be kept indefinitely, you can just convert it to a shared mailbox and grant the user with both Full Access and Send As permission. (No need to configure mailbox forwarding.) Reconfigure the user's Outlook profile by adding the "@company.com" only. Because of the default automapping feature, "@dep-companion.com" would show up automatically below the primary account. The user would be able to receive and respond to mails or meetings coming towards "@dep-companion.com" smoothly since Full Access and Send As permissions are assigned.

If the final goal is to deprecate the old email address "******@dep-companion.com", agree with Vasil that it'd be better to try merging the mailboxes and then assign the old address as an alias of the main mailbox:

1. For merging mailboxes, you can refer to the steps and discussions in the links below: Move/copy emails to a different mailbox
   How to Merge Exchange Online mailbox
2. Regarding transferring the alias to the main mailbox, basically you can follow the instructions in this document to release the alias "******@dep-companion.com" from the current shared mailbox and then add it to the main mailbox.

By the way, as regards to your concern about the automapping, yes, it's by default enabled when assigning Full Access. To disable it, administrator needs to use Exchange Online PowerShell to remove the full access permission and readding it by setting automapping to $false. See this link.
No option available in Exchange admin center. Afterwards, users can manually add the shared mailbox as an additional mailbox in Outlook client.

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