External Company replies 'On behalf of'

[Steven Hayes]

Hi Office365 Community,

I have a client with a really unusual issue. The client in question has sent out a number of meeting invites from their domain 'mycompany.com' and an external client with an entirely separate, unrelated domain (notmycompany.org) has responded to the invite with a message 'on behalf of' the original organiser. For example sally@mycompany.com received a response to her calendar invite from 'george@notmycompany.org on behalf of sally@mycompany.com'. Is this expected behaviour? I have not noticed this myself or with any other clients and I am wondering why this would be occurring.  I did not think it was possibly to act on behalf of a company outside of your own domain. Aside from general business these companies are in no way affiliated with one another so should not have the ability to act on behalf of each other. Is this something that should be raised with O365 support directly? The user is running Outlook 2016 for Mac and the client is up to date.

Thanks

[#2]

I think this is just normal behavior in the following situation:

1. User a@mycompany.com sends invitation to user a@notmycompany.org
2. User a@notmycompany.org forwards the invitation to b@notmycompany.org which will be "sent by a@notmycompany.org on behalf of a@mycompany.com"
3. User b@notmycompany.org accepts the invitation and a notification is sent to a@mycompany.com

[#3]

Thanks for your reply @Nestori Syynimaa

In this scenario the invite was not forwarded to another user rather the recipient responded directly to the organiser to say that they could not attend looking like this

1. User a@mycompany.com sends invitation to user a@notmycompany.org
2. User a@notmycompany.org responds to the invite from a@mycompany.com
3. User a@mycompany.com receives response and it appears as so: "a@notmycompany.org on behalf of a@mycompany.com".

I have tested this between office 365 clients internally and I could not replicate the issue. My client is concerned that this person has responded on behalf of herself and want's to verify that this cannot be replicated in any other way. But I cannot confirm this myself as I am unsure of the cause of the issue in the first place.

[#4]

Try to see from message trace where/how the response was delivered. You could also see the response email headers to track the mail delivery.

[#5]

We have checked the headers and cannot see anything out of the ordinary or anything to indicate why the response appears 'on behalf of'. In fact there is no mention of the recipient at all in the header so I am unsure why Outlook displays it this way. Additionally I have checked a third party client and since the 'on behalf of' feature is unique to Outlook it simply shows that the response is from the original sender of the invitation, not the recipient as it should be.

[#6]

After some deeper digging with Microsoft it became clear that the reason we were seeing the behaviour was in fact because the recipient of the original invitation, rather than replying to the event, actually forwarded it back to the meeting organiser. Since the event is being forwarded it appears on behalf of the original meeting creator. This is intentional as Microsoft want it to be clear who the meeting organiser is when events are forwarded. This way additional people can be invited to the event.