Office 365 groups is a cool feature introduced by Microsoft , this is diffrent from traditional distribution groups. When it is created members get
- Shared Inbox
- Shared calendar
- Shared Doc Library
- Shared One note
- Shared Teamsite
- Planner
I will not discuss it features as it has been documented well by Microsoft. Here we will discuss about the issues with Hybrid customers as they want interoperability.
One of our Customer is on Exchange 2010 & they want that on-premise users should be able to send email to office 365 groups. Now it becomes interesting as they need Group write-back feature which is part of Azure ad premium & they need to be at-least on exchange 2013.
Even if they are on Exchange 2013 they will still need to have Azure Ad premium.
https://technet.microsoft.com/en-us/library/mt668829(v=exchg.150).aspx
- Purchased Azure Active Directory Premium licenses for your tenant. This is required to enable the groups writeback feature in Azure Active Directory Connect.
- On-premises Exchange integration with Office 365 Groups is available in CU1 and newer releases of Exchange 2016, and CU11 and newer releases of Exchange 2013. However, Exchange hybrid requires the latest Exchange 2013 or Exchange 2016 Cumulative Update (CU) to be installed on your on-premises Exchange servers. If you can’t install the latest CU, the update released immediately prior to the current CU can be used.
There is a workaround that we can do or a customized power-shell scripting solution (which I will write if customer asks). This concept has already been discussed with Microsoft & they said yes we can do that.
Create a OU in on-premise environment with Name “Office 365 Groups”, edit the AAD connect to not synchronize this OU with azure AD.
Now for every Unified Group , I mean office 365 group just create a mail contact on on-premise where external address(Target address) will be pointing to route email to o365 group.
If groups are small in number we can manage this manually but these will constantly increase in number so you know the options 🙂
- Azure Ad premium with Exchange 2013
- Powershell customized solution.
Definitely, OOB will be better option but not for all so for other customers We can build Powershell based automated solution, lets see how much our customers require it , if we are pushed a lot than just wait for it, I will write & share the solution.
Thanks for reading
Tech Wizard
Tech Wizard 
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Hi,
I am trying to make it work with on-prem Exchange2010 SP3 and Office365 Group but no luck…
I need that on-prem users that are not members of the Office365 Groups can send emails to the group.
I created the OU “Office365Groups” and excluded it from AAD Connect
I created the mail contact on prem with this command:
New-MailContact -Name TestGroup -Alias testgroup -ExternalEmailAddress testgroup@company.mail.onmicrosoft.com -OrganizationalUnit Office365Groups
When an on-prem user sends email using the contact TestGroup it receives the following NDR message:
550 5.7.193 UnifiedGroupAgent; Delivery failed because the sender isn’t a group member or external senders aren’t permitted to send to this group.
What could be wrong?
Thank you,
Roberto
have you checked the error: Delivery failed because the sender isn’t a group member or external senders aren’t permitted to send to this group. as it seems your o365 group is restricted to members only..
Hi Vikas and thank you for your reply.
The group is private but that doesn’t means non members are not allowed to send emails.
Non members who have office365 mailboxes send emails to the group without any problem.
Only on prem users have problems as they are identified as users external to the organization.
Are you sure you didn’t change anything else on the connectors or the accepted domains etc.?
Thank you again,
Roberto
All our domains are verified/accepted in o365
I’m having the same issue. Did you ever get this figured out?
If I enable the option “Let people outside the organization send email to the group”, the emails seem to go thru and there is no NDR, however, the O365 group members never receive the email.. Either way, I rather keep the O365 group as internal senders only.
Thank you
Are you expecting the messages in user mailboxes as well, same as distribution lists ??
Send copies of group conversations and events to group members’ inboxes.(as in hybrid with 2010 you have to do that else emails will not reach the onprem mailboxes)
Be sure to check attribute named msExchRequireAuthToSendTo and set it to FALSE on O365 group synced back to on-prem OU. That will enable non-group members to send to the group.