Forum Discussion
Failed to send emails to outlook/hotmail recipients, returns error 550 5.7.515
We are supporting vendor of a public service, the system sends email notifications to patrons every day. The volume is around 20000-25000 emails per day. Recently, our mail server got large amount of bounced back emails (around 25%) that were not able to deliver to patrons with hotmail/outlook/live/msn email account.
From the returned "Diagnostic-Code: smtp;550 5.7.515", understand that it's because of the requirement of SPF (Pass), DKIM (Fail) and DMARC (Pass) authentication. However, currently our email infrastructure can't support the change of DKIM configuration. Can we request Microsoft to add our domain in whitelist and allow us to send emails to notify our patrons? Any way to contact hotmail/outlook/live/msn postmaster?
Please advise, thanks.
1 Reply
-- Recently, our mail server got large amount of bounced back emails
As far as I know the new mass mailer policy was put in place April 2025. Not sure why you are just now seeing the impact.
-- that it's because of the requirement of SPF (Pass), DKIM (Fail) and DMARC (Pass) authentication
Part of High Volume Policy and also in Anti-phishing policies
https://learn.microsoft.com/en-us/defender-office-365/anti-phishing-policies-about
-- Any way to contact hotmail/outlook/live/msn postmaster?
https://substrate.office.com/ip-domain-management-snds/postmaster/
