Fix "550 5.7.509": Outlook/Microsoft rejected the message for failing DMARC

If your email is bouncing with 550 5.7.509, it means Outlook/Microsoft rejected the message for failing DMARC. Here is exactly what causes it and how to fix it.

What 550 5.7.509 means

Microsoft returns 5.7.509 when your mail does not pass DMARC. Outlook and Office 365 are strict about alignment and will reject rather than spam-folder unaligned mail.

How to fix 550 5.7.509

• Align SPF or DKIM with your From domain and publish DMARC.
• Register at the Microsoft SNDS/JMRP programs to monitor reputation.
• Remove any unaligned third-party senders from your domain.

How Rainmail helps

Rainmail sends from your own domain on a dedicated, isolated IP with SPF, DKIM, DMARC, reverse-DNS and managed warm-up handled for you, plus an AI that watches your list health and deliverability. It also welcomes the senders Amazon SES, SendGrid and Mailchimp reject — from $8, cheaper per email than SES. Run the free 10-second checker or see plans.