I have a Domino server that is configured with a relay host for mailing to members on the Internet. Now suddenly all mails sent from the Domino server cannot be delivered and are giving me this error: "Error transferring to Mail.ISP.com; SMTP Protocol Returned a Permanent Error 550 5.1.7 Invalid address."
While troubleshooting, I tried sending a mail from Outlook in the same server and it is delivered properly. So it is confirmed that SMTP ports are open. Could you please suggest a way to solve this problem?
Sounds like your ISP has changed its settings and thinks that you are spamming them. You will have to work with them to resolve.
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