Your offers and invoices are useless if they land in the recipient's spam folder. Most deliverability problems are caused by missing or incorrect email authentication.

SPF – Sender Policy Framework

A DNS record that lists which servers may send email for your domain. If you send through several services (your mail server, a newsletter tool, a CRM), all must be included – within the lookup limits.

DKIM – DomainKeys Identified Mail

Outgoing emails are digitally signed. The receiving server checks the signature with a public key in your DNS. It proves the email wasn't altered and really comes from your domain.

DMARC

DMARC tells receiving servers what to do if SPF or DKIM checks fail – monitor, quarantine or reject – and sends you reports. Major email providers now expect DMARC, especially for senders of larger volumes.

A typical rollout:

  1. Start with p=none and collect reports
  2. Fix all legitimate sending sources
  3. Move to quarantine, then reject

Other deliverability factors

  • Consistent sender names and addresses
  • Clean newsletter lists with double opt-in
  • Easy unsubscribe options
  • Avoiding spam-like content and too many links
  • A good reputation of your sending IP and domain
  • Correct reverse DNS for your mail server

Testing

Send test emails to different providers and check headers, or use deliverability testing tools. DMARC reports show who sends email in your name – sometimes revealing forgotten tools or abuse.

Who should set this up?

DNS changes can break email if done incorrectly. With our Managed Hosting and IONOS Management, SPF, DKIM and DMARC are configured and checked as part of the service.

Planning a project like this? Our AI project assistant asks the right questions for your field and turns your answers into a clear brief – then our team near Munich sends a free, non-binding quote within 24 hours on business days. Start now or read the complete Hosting & IT Infrastructure guide.
#Email#SPF#DKIM#DMARC#Deliverability