Problem with send e.mail

Problem with send e.mail

Hi ,
from last saturday I can't send the e.mail and receive the mail ticket.
the message is:
Invio e-mail non riuscito. Command : MAIL FROM:, Return Code : 530, Response : 530 5.7.1 Client was not authenticated

The request are in servidesk when the user send the e.mail

Any idea?

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