imap smtp - window live mail errore 0x800CCC69 stesse identiche impostazioni thunderbird nessun errore

ambiente exchange 2013 client esterno che si connette in imap smtp.

thunderbird funziona correttamente 

Da windows live mail il sistema segnala il seguente errore:

Server Response: 550 5.7.1 Client does not have permissions to send as this sender

nel log del connettore trovo la seguente situazione

2014-07-15T13:52:18.456Z,CAS\Client Frontend CAS,08D1448A8AB29CBF,39,*.*.*.*:587,*.*.*.*:35136,*,mydomain/postmaster33,authenticated
2014-07-15T13:52:18.565Z,CAS\Client Frontend CAS,08D1448A8AB29CBF,40,*.*.*.*:587,*.*.*.*:35136,*,,Proxy session was successfully set up. Session mydomain/postmaster33 will now be proxied
2014-07-15T13:52:18.565Z,CAS\Client Frontend CAS,08D1448A8AB29CBF,41,*.*.*.*:587,*.*.*.*:35136,>,235 2.7.0 Authentication successful,
2014-07-15T13:52:18.931Z,CAS\Client Frontend CAS,08D1448A8AB29CBF,42,*.*.*.*:587,*.*.*.*:35136,-,,Remote(SocketError)