eDiscovery/Content Search

[Steve Cant]

Hi, We're in the process of migrating from on-prem exchange to O365, having already moved achiving online some time ago. 

I would like to use eDiscovery or a Content Search.  Can these be utilised to search across on-prem Exchange as well as O365 in the form of say an on-prem mailbox with the mail archive in O365 ?

I have tried adding a mailbox to search which has not yet been migrated and it does not return a mailbox.

any advice greatly appreciated

[#2]

Only if you are in Hybrid (with 2013+ servers and OAuth configured): https://technet.microsoft.com/en-us/library/dn497703%28v=exchg.150%29.aspx

[#3]

Thank you Vasil.