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Email Deliverability and DMARC

  • Updated

Overview

Deliverability issues—like emails landing in spam, getting blocked, or not arriving—are often tied to sender reputation and authentication. DMARC, SPF, and DKIM help verify your domain’s legitimacy. Misconfiguration or poor list hygiene can trigger sender blocks and hurt delivery rates.

What Is DMARC and Why It Matters

DMARC (Domain-based Message Authentication, Reporting & Conformance) builds on SPF and DKIM to protect your domain from spoofing. It checks if the visible From address aligns with the technical sending domain (MailFrom/return-path). If alignment fails, recipient mail servers may block or filter your message.

Key Requirements for Heymarket:

  • SPF and DKIM must be correctly configured
  • DMARC policy should support relaxed alignment (aspf=r), as strict alignment can cause delivery failures
  • If you already have a DMARC record with a non-default policy such as quarantine or reject, you may keep your existing record as it provides full DMARC benefits — our suggested SendGrid DMARC is advisory only

Impact on Outbound Emails (Sending from Heymarket)

Heymarket sends through your authenticated domain via SMTP. A misconfigured DMARC record or bad sender reputation can cause:

  • Hard blocks (rejected by the recipient server)
  • Silent filtering (emails routed to spam or discarded)

What to Do

  • Verify DNS records (SPF, DKIM, DMARC) are published and valid
  • Use a relaxed aspf=r policy in your DMARC record
  • Monitor bounce reports and error logs for block-related issues
  • Avoid frequent sending to unengaged lists
  • Our suggested SendGrid DMARC record is primarily for new domains and does not replace existing non-default DMARC configurations

Sender Blocks Explained

A sender block is when the recipient’s mail server outright rejects your message—often before it reaches the inbox. This typically results from:

  • Failing DMARC/SPF/DKIM
  • Low sender reputation (spam complaints, unsubscribes, poor engagement)
  • Appearance on blocklists or blacklists
  • Spam-like content or formatting

Prevention Tips:

  • Keep list hygiene clean (remove unengaged/inactive users)
  • Avoid misleading subject lines and spammy formatting
  • Use consistent branding and tone
  • Check IP/domain block status via tools like MXToolbox

Impact on Inbound Emails (Forwarding to Heymarket)

If your system forwards messages using a customer’s email as the “From” address, this may break DMARC rules—especially if the domain isn’t yours. Forwarding services or mail relays may block the message before Heymarket receives it.

Heymarket Behavior:

  • We don’t block based on DMARC
  • We do rely on what forwarding services allow

Recommendation:

  • Use your own domain in the “From” field
  • Set the customer’s email in the Reply-To field

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