Official DNS Guide • Developer Transactional Email & React Email

Resend (Modern Developer Email API) SPF Record Setup & Validator

Step-by-step guide to configure Resend SPF records (include:resend.com), 2048-bit DKIM TXT keys, and DMARC alignment for modern apps.

Quick Answer • Exact Resend SPF Syntax

To authorize Resend (Modern Developer Email API) to send emails on behalf of your domain, add include:resend.com to your domain's single DNS TXT SPF record before the terminating ~all mechanism. The standard record is v=spf1 include:resend.com ~all.

Live Resend DNS Validator

Test your domain's published SPF, DKIM, and DMARC records via global DoH edge nodes in real time.

Zero-Log Client Evaluation

Understanding Resend (Modern Developer Email API) Email Authentication

Resend is the developer-first email API for Next.js, Remix, and modern web applications. Resend enforces custom domain verification with strict SPF and DKIM authentication to ensure 100% inbox delivery and DMARC alignment.

When Resend (Modern Developer Email API) delivers outbound emails on your behalf, recipient mail transfer agents (MTAs) at Google, Yahoo, Microsoft, and corporate mail gateways inspect the sender identity. Without a published SPF record explicitly permitting Resend (Modern Developer Email API)'s IP ranges, these emails trigger SPF Softfail (~all) or Hardfail (-all), severely degrading domain reputation and inbox placement.

Required DNS Records for Resend

Publish the following DNS records in your domain registrar or DNS management console (Cloudflare, AWS Route 53, GoDaddy, Namecheap):

TypeHost / NameValue / TargetTTLPurpose
TXT@v=spf1 include:resend.com ~all3600Authorizes Resend infrastructure.
TXTresend._domainkeyv=DKIM1; k=rsa; p=MIIBIjANBgkqhki...3600Resend 2048-bit DKIM signature key.
TXT_dmarcv=DMARC1; p=reject; rua=mailto:dmarc@yourdomain.com3600DMARC anti-spoofing policy.

Step-by-Step Setup Instructions

1

Log in to Resend Console > Domains > Add Domain.

2

Enter your apex domain (e.g. yourdomain.com) or dedicated sending subdomain (e.g. mail.yourdomain.com).

3

Copy the DKIM TXT record at "resend._domainkey" and add it to your DNS.

4

Add the SPF TXT record with "v=spf1 include:resend.com ~all".

5

Add the MX and feedback tracking records provided by Resend.

6

Click Verify DNS in Resend dashboard.

Common Resend SPF Configuration Mistakes

× MX Record Overwrite Risk

Cause: Publishing Resend MX records on an existing corporate email domain.

Fix: Use a sending subdomain (e.g. mail.yourdomain.com) if apex domain already has Google Workspace or M365.

Frequently Asked Questions

What is the SPF include string for Resend?

The SPF mechanism is "include:resend.com".

Should I use a subdomain for Resend?

Yes, using a subdomain (e.g. updates.yourdomain.com) isolates transactional reputation from corporate inbox MX records.