550 5.7.1 — Message rejected under suspicion of spam (Yandex)
Retrying will not help. The message will not be delivered.
The reply
550 5.7.1 Message rejected under suspicion of SPAM.Yandex refused the message on its own filtering. Authentication is the first thing to check here, because Yandex treats an unsigned or unaligned message from an unfamiliar domain far more harshly than most.
What it means
A permanent rejection combining the domain's reputation at Yandex, the complaint rate from its users and the message content. Yandex weighs DKIM particularly heavily: mail from a domain with no signature and no history is close to undeliverable at volume, whatever the content says.
Why it happens
- No DKIM signature, or one that does not align with the From: domain.
- A domain with no sending history at Yandex.
- Complaints from Yandex users on earlier mail.
- Bulk-looking content, or links through a shortener.
- Mail to a list that did not confirm its subscription.
What to do
- Set up DKIM signing aligned with the From: domain, and confirm it in the postmaster dashboard.
- Register the domain at postmaster.yandex.ru to see reputation and complaints directly.
- Publish SPF and a DMARC policy alongside the DKIM key.
- Reduce volume while the domain establishes itself.
- Add a working unsubscribe and remove anyone who has complained.
Questions
Everything else accepts my mail.
Yandex weighs DKIM and domain familiarity more heavily than most receivers, so a domain that is merely new can be refused here while passing elsewhere. Check the signature aligns before looking at content.