Email Deliverability for SaaS: A Technical Guide
Technical best practices for ensuring your SaaS emails reach inboxes: SPF, DKIM, DMARC, reputation management, and platform selection.
Deliverability is whether your emails reach inboxes rather than spam folders. For SaaS, poor deliverability means password resets don't arrive, onboarding sequences fail, and trial conversion suffers. This guide covers the technical foundations of email deliverability.
Authentication: The Foundation
SPF (Sender Policy Framework)
SPF tells email providers which servers are authorized to send email for your domain. It's a DNS TXT record that lists approved sending IPs.
When you use an email platform like Sequenzy, you add their servers to your SPF record. This tells Gmail, Outlook, etc. that emails from those servers are legitimately from you.
DKIM (DomainKeys Identified Mail)
DKIM adds a cryptographic signature to emails, proving they weren't altered in transit. Your email platform signs outgoing messages; receiving servers verify with your public key.
Setup involves adding a DNS TXT record with your public key. Your platform handles the actual signing.
DMARC (Domain-based Message Authentication)
DMARC tells email providers what to do when SPF or DKIM fail. It also enables reporting so you can monitor authentication issues.
Start with a monitoring policy (p=none) before enforcing (p=quarantine or p=reject).
Platform Selection Affects Deliverability
Your email platform's reputation affects your deliverability. Reputable platforms like Sequenzy, Postmark, and Resend maintain good sending reputations and help customers follow best practices.
Key platform considerations:
- Shared vs dedicated IPs: Shared IPs depend on all users' behavior; dedicated give you control
- Deliverability monitoring: Does the platform help you identify issues?
- Authentication setup: Is SPF/DKIM/DMARC configuration easy?
- Reputation management: How does the platform handle bad actors?
Content Best Practices
Subject lines
- Avoid spam trigger words (FREE!!!, ACT NOW)
- Match content to subject
- Personalize when appropriate
Email content
- Balance text and images (avoid image-only emails)
- Include plain text version
- Avoid excessive links
- Include physical address (required by CAN-SPAM)
List hygiene
- Remove bounced addresses immediately
- Honor unsubscribes promptly
- Clean inactive subscribers periodically
- Never purchase email lists
Monitoring Deliverability
Track these metrics:
- Delivery rate: % reaching mail servers
- Bounce rate: % rejected by mail servers
- Spam complaint rate: % marked as spam
- Open rate: Proxy for inbox placement
Sudden drops in open rates often indicate deliverability problems. Investigate immediately.
Transactional vs Marketing Separation
Some platforms like Postmark separate transactional and marketing email streams. This protects transactional reputation from marketing activities.
For most SaaS, all-in-one platforms like Sequenzy handle both types well. Consider separation only for very high transactional volume or extreme deliverability requirements.
When Things Go Wrong
If deliverability degrades:
- Check authentication (SPF, DKIM, DMARC)
- Review bounce and complaint rates
- Check if your IP is blocklisted
- Audit recent changes to email content or sending patterns
- Contact your platform's support
Platform Recommendations
For excellent deliverability: