While the Forefront Identity Manager Service did connect and authenticate with the Exchange Web Service, its credentials ...

While the Forefront Identity Manager Service did connect and authenticate with the Exchange Web Service, its credentials are not sufficient to perform necessary operations in the mailbox.

The most likely cause is the Forefront Identity Manager Service's account only has read permissions when both read and write permissions are required.

The Forefront Identity Manager Service cannot connect to the SQL Server because its credentials were rejected.