On creating a new distribution group in Exchange you could get the following error:

Couldn’t find object “<user object in AD>”. Please make sure that it was spelled correctly or specify a different object. Reason: the recipient <user object in AD> isn’t the expected type.

You probably logged in with an administrator account, which has no mailbox associated with it. When you create a mailbox,  you will automatically be the manager of the distribution group.

To bypass this (without creating a admin user mailbox), use the powershell command: New-DistributionGroup and specify the “ManagedBy” parameter