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...
-- 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/