If you use Microsoft Exchange as a mail relay for other servers, and on the server from which you send mail, you have an error
Relay = exchangerelay.domain.com [10.10.10.10]: 25, delay = 5.1, delays = 0.04 / 0.01 / 0.05 / 5, dsn = 5.7.1, status = bounced (host exchangerelay.domain.com [10.10.10.10] Said: 550 5.7.1 Unable to relay (in reply to RCPT TO command))
Check the Exchange Relay Connector settings. You need to make sure that the IP address of your server is in the list of addresses from which mail is allowed to receive.
Open the Microsoft Exchange Console, navigate to Server Configuration -> Hub Transport
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