Exchange 2010 - Get-Mailboxpermission and security groups

Hi all,

Apologies in advance if this question has been asked before however i'm failing to find any resources online about it.

I am doing a migration from Exchange 2010 > Office365 and need to run a report about who has access to what mailboxes.

The issue i have is that using "Get-Mailboxpermission mymailbox@mydomain.com" returns values which may contain security groups. The report then returns that the group has full access permission, But does not enumerate the users contained in the group.

As 90% + of our permissions are granted this way, I need an easy way to enumerate this.

Unfortunately, The "Get-Adgroupmembers" cmdlet does not accept identities in the format of "Domain\Group" only "Group" or "SID" or "LDAP string"

Has anyone run into a situation like this before and or have a script available that performs the above action?

Thanks in advance

Chris