Relaying occurs when an e-mail message is sent to an e-mail address whose domain (the name after the @ symbol, such as adatum.com) is not processed by the Simple Mail Transfer Protocol (SMTP) or outgoing server that the sender is requesting to deliver the message. The SMTP server must connect to another SMTP server to relay the message. When you send an e-mail message that encounters a relay error, your SMTP (outgoing) e-mail server might return your e-mail message with an error message such as one of the following:

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