Calendar sharing detail vs generic "free/busy" in a hybrid Exchange migration

I am in the beginning phase of a hybrid migration from Exchange 2007 to Office 365 using two 2013 servers for the hybrid role. We have two Exchange 2007 servers in two separate sites. Both of the 2013 servers are in Site A, if it makes any difference.

I have migrated 15 mailboxes from on premise to O365. After doing so, the migrated end users are noticing that they are having to re-share their calendar, as people who could previously see detail now are only able to see "Busy". Also, they are noticing that they cannot see on-premise calendar detail until after the on-premise individual has re-shared their calendar with the O365 user.

So, the first question - is this to be expected, or is there a way to circumvent this prior to the mailbox being migrated?

Additionally, on-premise users who had access to a migrated user's mailbox prior to the migration, are being prompted for credentials in order to access the calendar of the migrated user. again, is this to be expected, or is there some way to mitigate this? Is this where the Online Services Sign-in Assistant comes into play?


JonathanSpitfireSenior Solutions EngineerAsked:
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Vasil Michev (MVP)Commented:
Moving the mailbox to EO is essentially moving it to a new organization, you will have to readjust the permissions. As for mailbox permissions, they are not really supported cross-premises. They might work in some cases, but the general rule is if you want to keep mailbox permissions, move the owner and delegate mailboxes in the same batch.
JonathanSpitfireSenior Solutions EngineerAuthor Commented:
I'm not talking about delegates - I am talking about simply sharing calendar detail.

The interesting thing is that the affected user is able to see calendar detail for some on premise calendars, but not for others....but he had the ability to see those others before he was migrated.

I'm opening a case with Microsoft to get some answers.
JonathanSpitfireSenior Solutions EngineerAuthor Commented:
As it turns out, free busy DETAIL is not supported between 2007 and O365. This is not well documented by Microsoft. while it is possible to see generic free/busy/tentative, that's the best you'll get between and on-premise user and an O365 user when the on premise user is on exchange 2007. This was confirmed by Microsoft.

so, when asking about Free/busy, be sure to state, "free/busy DETAIL" as many people assume that free/busy means free/busy detail. Trust me, it doesn't, and we got burned by lack of documentation from Microsoft (and thorough testing, I suppose).


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JonathanSpitfireSenior Solutions EngineerAuthor Commented:
because my solution is the most complete and accurate one. awarding points to Vasil because his information was accurate and he took the time to answer, however he did not answer my question.
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