Another post office has been closed because of mold.   After a Postal Service inspection team disocvered mold in the post office on Somerset Avenue in Princess Anne, Maryland, postal officials decided to shut down the building for the safety of customers and workers, said Yvette Singh, a spokeswoman for the USPS in Baltimore.  Postal workers have been servicing customers since Saturday from a mobile unit stationed in the rear of the post office facing Church Street.  Read more.