Migration of contacts is slow when user has PDLs that include many external users, Error "The server cannot service this request right now"
When migrating a user with Personal Distribution Lists (PDLs) that include many external users you may experience slowness and "The server cannot service this request right now" errors in the migration log file.
This issue occurs because On Demand Migration for Email (ODME) is attempting to resolve the external contacts in the PDL to objects in the target environment.
An Enhancement Request, PT 110639962, has been logged for this issue and is waiting for a fix in a future version of On Demand Migration for Email.
After further investigation, this issue may be related to Active Directory sync issues in a federated environment with Office 365.