Hi, it seems like one of your mailservers have been blacklisted. I have not received some emails that are sent and they are getting Error
Below is the message they get when they email me. according to MXtoolbox this is missing DMARC check
Error Details
Error: 550 5.0.350 Remote server returned an error -> 552 1 Requested mail action aborted, mailbox not found
Message rejected by: mtaproxy203.free.mail.ir2.yahoo.com
Notification Details
Sent by: DB8PR04MB6970.eurprd04.prod.outlook.com
James anda
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Hi. Thank you for writing to us. Please be advised that Yahoo is protecting you by prioritizing authenticated email. The small business or domain that is trying to email you needs to update its DKIM settings/security with its email provider. We can help you inform the sender about the problem, but unfortunately, we can't directly fix the issue ourselves. Let the sender know there's an authentication issue on their end specifically with DKIM (DomainKeys Identified Mail).
Recommend they configure DKIM for their emails. Direct them to go to https://learn.microsoft.com and search for Email Authentication in Microsoft 365.
They can contact Microsoft directly for DKIM setup assistance. We apologize for the inconvenience and appreciate your patience while Microsoft resolves this issue.