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.
Dig deeper on Domino Resources - Part 7
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