unsupported email address

Have been using em-client successfully with outlook.com account for some time but have now started receiving this error and contacts folder loads a few contacts and then stops. Have tried updating to latest version of emclient, removing account and reinstalling, creating account in emclinet on another laptop.  I downloaded the contacts folder from www.outlook.com and spotted one “unidisclosed recipient” which I deleted from www.outlook.com people folder.   Still getting the error message

I remembered that I had Scheduled Back Ups switched on.   Restored to a date before the problem arose and now the Outllok.com accounts syncs OK.