When clicking on a synched user identity in O365 you receive the following Correlation ID error.
This can be cause by two of the following issues.
1. User has been assigned an Exchange Mailbox but has not been assigned a license yet
2. User has an Exchange Archive disabled on-prem but is enabled in Exchange online. Resolution is to also enable the Archive on-prem and then allows Azure AD Sync to synch the attributes then the error should disappear.
To identify the cause and get further details of the error you can run the following command in the O365 Powershell:
(Get-MsolUser -UserPrincipalName temp.user1@domain.co.uk).errors[0].ErrorDetail.objecterrors.errorrecord.ErrorDescription
Get-MsolUser -HasErrorsOnly | ft DisplayName,UserPrincipalName,@{Name="Error";Expression={($_.errors[0].ErrorDetail.objecterrors.errorrecord.ErrorDescription)}} -AutoSize