Access to an Exchange 2007 Calendar from Office 365

btny
btny used Ask the Experts™
on
Hello,

We have a client who currently runs Exchange 2007 and has 2 organizations using it.  (so 2 email domains).  One of those organizations will be splitting off and getting their own Offfice 365.  There wont be any hybrid setup the Office 365 will be fully cloud.

We have about 5 conference rooms here in the office which are setup as Room Calendars in the Exchange 2007.

Is it possible to somehow make it so users in the Office 365 can view those Exchange 2007 room calendars?  Even better, is it possible for someone from the Office 365 to edit one of those Exchange 2007 calendars.

Last note, these would be two separate domains
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Senior Systems Admin
Top Expert 2010
Commented:
On whether it's possible to make users view calendars for on-prem mailboxes, yes, it's possible, but doing so requires that you have an Exchange 2010 CAS server in your environment that is connected to the MS Federated Gateway. Office 365 doesn't support the availability features of Exchange 2007, so there is no way to get the two systems to communicate without at least one 2010 SP3 server on-prem.

On if it's possible to modify on-prem mailboxes from the cloud, not directly. If you have an on-prem mailbox that users add to their outlook profiles (with Outlook 2010+) they could open the calendar and edit it with that account, but there is no way to allow mailbox permissions for Office 365 mailboxes to On-prem mailboxes.
Most Valuable Expert 2015
Distinguished Expert 2018

Commented:
Don't think it will be possible. The only thing you can do in such scenario is to publish the calendars somewhere (Office Online)
Jeffrey Kane - TechSoEasyPrincipal Consultant
Most Valuable Expert 2016
Top Expert 2014

Commented:
You should be able to do it:

On your Exchange 2007 run this command:
Set-MailboxCalendarSettings <resource mailbox name> -processexternalmeetingmessages $true

Then, create the contact records for each user you are moving to Office365.

The Office 365 users should then be able to block space on the Conference Room Calendar.

To make it easier for them, you can publish the calendar

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