Email Authentication (SPF, DKIM, DMARC):

Authentication is the foundation of deliverability. Gmail, Yahoo, and Microsoft (as of May 2025) require proper authentication for bulk senders. Authenticated senders are 2.7x more likely to reach the inbox.

SPF (Sender Policy Framework):

Specifies which servers can send email for your domain. Add include:_spf.salesforce.com to your DNS TXT record. Maintain a single SPF record with a maximum of 10 DNS lookups.

DKIM (DomainKeys Identified Mail):

Adds a cryptographic signature verifying message integrity. Generate DKIM keys in Salesforce Setup → Email Administration → DKIM Keys, then add CNAME records to DNS. Use minimum 1024-bit keys (2048-bit recommended).

DMARC (Domain-based Message Authentication, Reporting & Conformance):

Enforces SPF/DKIM and provides reporting. Start with p=none for monitoring, then progress to p=quarantine and p=reject. Only 18% of top domains have valid DMARC—proper implementation provides a competitive advantage.

List Hygiene & Management:

Poor list quality is a primary driver of deliverability issues. Implement these practices: • Remove hard bounces immediately—keep bounce rates under 2% (ideally under 0.5%) • Review inactive subscribers every 3-6 months; implement sunset policies for 6+ month non-engagers • Use double opt-in for new subscribers to ensure valid addresses • Validate email addresses at the point of entry using verification tools • Never send to purchased lists—this triggers spam complaints and damages reputation • Clean lists monthly or quarterly (Microsoft recommendation)

Gmail/Yahoo Requirements (2024+):

Since February 2024, Gmail and Yahoo have enforced strict requirements for bulk senders (5,000+ emails/day): • SPF or DKIM authentication required; DMARC required for bulk senders • Spam complaint rate must stay under 0.3% (Gmail recommends under 0.1%) • One-click unsubscribe required (RFC 8058 compliant) with 48-hour processing • Domain alignment with DKIM signature or SPF envelope sender • Microsoft enforces similar requirements starting May 2025

Sender Reputation Management:

Your sender reputation is the score ISPs assign based on sending practices: • Use dedicated IP for 100,000+ emails/month (requires IP warming) • Monitor reputation via Google Postmaster Tools and Microsoft SNDS • Register for ISP feedback loops to receive spam complaint notifications • Maintain consistent sending volume—avoid sudden spikes • Use a custom sending domain matching your brand for trust

Content & Engagement Optimization:

ISPs evaluate engagement signals to determine inbox placement: • Write descriptive subject lines—avoid generic phrases like "Hey!" that trigger spam filters • Personalize content with recipient names and relevant details • Segment audiences for targeted, relevant messaging • Include clear, visible unsubscribe links in every email • Balance text-to-image ratio; avoid image-only emails • Test emails across Gmail, Outlook, Yahoo before sending

Monitoring & Testing:

Track these key metrics continuously: • Bounce rate: Target under 2% • Spam complaint rate: Under 0.1% (never exceed 0.3%) • Open rate and click-through rate: Engagement signals • Inbox placement rate (via seed testing) • Use Setup → Email Administration → Test Deliverability in Salesforce

Key Takeaways

  • Configure SPF, DKIM, and DMARC authentication—authenticated senders are 2.7x more likely to reach the inbox
  • Maintain spam complaint rates under 0.1% and bounce rates under 2% to protect sender reputation
  • Clean lists every 3-6 months; remove 6-month non-engagers and hard bounces immediately
  • Deliverability is ongoing—monitor metrics continuously and adapt to evolving ISP requirements

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