Table of Contents
Introduction
Understanding email authentication basics
Emails not landing? It’s usually misconfigured SPF or missing DKIM, not your copy. Here’s the no‑fluff setup that makes FluentSMTP actually authenticate your domain and stop getting flagged as spoofed.
Why SPF and DKIM matter for deliverability
SPF designates approved sending servers for your domain, while DKIM attaches a verifiable signature to each message. Together, they reduce the chance of legitimate emails being marked as spam and improve trust with recipient servers.
Configure SPF for your domain
What SPF does and when to use it
SPF lists the servers that are authorized to send emails on behalf of your domain. It helps receiving mail servers distinguish legitimate messages from spoofed ones. Use SPF when you rely on multiple sending providers or your website’s mail function, such as WordPress plugins, transactional email services, or hosting mail servers.
Apply SPF to reduce bounce and misdelivery, and to improve inbox placement for your essential communications with customers and partners.
Publishing an SPF record in DNS
To publish an SPF record, add a TXT entry to your domain’s DNS zone. The record should specify allowed sending sources, for example listing hosting providers and third party services you use.
After publishing, verify the record with a lookup tool and monitor for any syntax issues that could invalidate the policy.
Publish DKIM records for trusted sending
The role of DKIM in email integrity
DKIM adds a cryptographic signature to outgoing messages, allowing recipient mail servers to verify that content has not been altered in transit and that it comes from your domain. The signature is created with a private key and checked against a public key published in your DNS records. When verification succeeds, trust is established and deliverability improves.
Using DKIM alongside SPF helps protect your domain from spoofing and phishing attempts, reinforcing your brand’s credibility with customers and partners.
Generating and publishing DKIM keys
- Generate a public private key pair via your SMTP provider or hosting control panel.
- Publish the public key as a DKIM TXT record in your domain’s DNS with the selector name you choose.
- Configure your mail system to sign outgoing messages with the corresponding private key.
- Test DKIM by sending messages to a mailbox that reports DKIM results or using a verification tool.
Link FluentSMTP to your DNS records
Verifying DNS changes
After publishing SPF and DKIM records, verify they are visible publicly. Use a DNS lookup tool to confirm the TXT records exist and that the DKIM selector matches FluentSMTP expectations. Ensure the SPF record lists all sending sources from FluentSMTP settings. Once verification shows as propagating, test sending a transactional email to confirm deliverability.
Common DNS pitfalls to avoid
- Not including all sending sources in the SPF record
- Using multiple DKIM selectors for the same domain without alignment
- Exceeding SPF lookup limits by listing too many domains or include mechanisms
- Misplacing DNS records in the wrong zone or using a CNAME where a TXT is required
Conclusion
Configuring SPF and DKIM strengthens email trust and improves inbox placement. After publishing the records and linking FluentSMTP to your DNS, perform end-to-end tests across providers to verify deliverability.
- Verify SPF includes all sending sources
- Confirm DKIM selector aligns with your setup
- Run end-to-end tests with multiple mailbox providers
