Email Deliverability Best Practices for 2026

When paid media, outbound, and email marketing operate in silos, no one manages sender reputation holistically. The result: emails that never reach prospects' inboxes, undermining product launches, event follow-ups, and content promotion across every campaign.

For SaaS companies with $20K+ ACVs, each missed inbox placement represents a lost pipeline. Yet deliverability rarely gets cross-functional attention. Marketing runs campaigns with one ESP, sales uses a separate outbound tool, and automated sequences run through yet another platform. Without coordination, the compounding damage to sender reputation goes unnoticed until pipeline suffers.

These six practices form the foundation for email deliverability in 2026.

1. Implement mandatory authentication protocols

SaaS companies sending 5,000+ emails per day to Gmail or Yahoo recipients must comply with mandatory authentication requirements. This covers marketing, transactional, and automated emails.

Three protocols form your deliverability foundation:

• SPF (Sender Policy Framework) specifies which mail servers can send email on your domain's behalf. Your ESP provides the exact record to add to DNS. Without SPF, receiving servers have no way to verify your emails are legitimate.
• DKIM (DomainKeys Identified Mail) adds cryptographic signatures verifying emails haven't been tampered with in transit. This protects both your reputation and your recipients from spoofed messages.
• DMARC (Domain-based Message Authentication) ties SPF and DKIM together and tells receiving servers what to do with emails that fail authentication. Start with a monitoring policy (p=none), then progress to p=quarantine and eventually p=reject over 60-90 days as you verify legitimate emails are passing.

Gmail and Yahoo enforce these requirements with spam folder placement or outright rejection for non-compliant emails. Bulk senders must also process unsubscribes within 48 hours with one-click functionality.

Implementation typically requires 1-2 hours working with your ESP and DNS administrator. The technical setup is straightforward. The challenge is ensuring authentication covers all email types across your organization rather than treating marketing, sales, and transactional email separately. This is required infrastructure before content optimization makes sense.

2. Optimize specifically for Microsoft Outlook

Microsoft Outlook shows lower inbox placement than consumer-focused providers like Gmail. For B2B SaaS targeting enterprise buyers, this creates a significant gap in reaching decision-makers.

The discrepancy exists because Microsoft's filtering algorithms weigh different signals than consumer providers. Enterprise email systems also layer additional filtering through Microsoft 365 and Exchange, creating multiple opportunities for legitimate emails to get caught.

This gap requires Outlook-specific optimization. Monitor Outlook performance separately from other providers in your email analytics. Test campaigns specifically to Outlook addresses before broader sends. Pay attention to formatting that renders differently in Outlook's older rendering engine.

When coordinating across sales and marketing, ensure both teams understand Outlook-specific deliverability challenges. SDRs sent from Outlook need the same authentication and reputation management as marketing automation.

3. Maintain aggressive list hygiene

Poor list hygiene damages sender reputation, causing future emails to land in spam. B2B email lists decay continuously as people change jobs, companies restructure, and email addresses become inactive. This cleanup requires ongoing attention.

Remove subscribers with no engagement based on your sending cadence:

Remove subscribers with 12+ months of inactivity regardless of sending frequency to avoid spam trap hits. Spam traps are email addresses that mailbox providers use specifically to identify senders with poor list hygiene; hitting one severely damages your sender reputation.

Critical bounce rate thresholds to monitor:

• Target: Below 0.5% indicates best-in-class list quality
• Warning: Above 2% signals hygiene issues requiring immediate attention
• Critical: Above 5% triggers mailbox provider filtering or blocking

Remove hard bounces within 24 hours, unsubscribes within 10 business days per CAN-SPAM requirements, and invalid addresses as soon as detected. Before removing inactive subscribers, send a targeted re-engagement campaign with preference center options and clear opt-out. Remove non-responders after 2-3 attempts.

Quarterly cleaning, approximately 4 hours per quarter, protects your entire email program. Cross-functional coordination ensures list hygiene protects the pipeline across marketing campaigns, sales outreach, and automated sequences.

4. Segment by engagement for technical deliverability

Modern mailbox providers use engagement-based filtering, creating a direct link between content relevance and technical deliverability. Poor engagement leads to lower sender reputation, spam folder placement, and worse future deliverability. This cycle affects even emails to genuinely interested prospects.

Segment lists by engagement windows to maintain strong sender reputation:

• 30-day window: Highly engaged subscribers who opened or clicked recently. This is your highest-value segment for new campaigns and product announcements.
• 90-day window: Moderately engaged subscribers showing declining interest. Send targeted re-engagement content before considering removal.
• 180-day window: Low engagement indicating potential list decay. Final re-engagement attempt before removal to protect sender reputation.

These segments help you maintain a strong sender reputation while maximizing reach to genuinely engaged prospects. The engagement data also informs content strategy: if certain segments consistently underperform, the content may not match their interests or stage in the buyer journey.

Coordinate engagement tracking across marketing nurtures, sales sequences, and automated campaigns. When these operate in silos, you lose visibility into how prospects engage across touchpoints, and sender reputation management becomes fragmented.

5. Enforce the 3-contact-per-company rule

B2B senders should limit outreach to 3 contacts maximum per company. Sending to multiple contacts simultaneously signals bulk spam to corporate email systems, particularly Microsoft 365 and Google Workspace.

This is a common failure mode when SDRs, marketing automation, and ABM campaigns operate independently. Without cross-functional visibility, the sales team emails 8 contacts at a target account while marketing automation sends to 5 more. The receiving company's email system sees 13 emails from your domain in a short window and flags you as a bulk sender.

The consequences extend beyond that single account. Corporate email systems share reputation data, and patterns of bulk sending to multiple contacts damage your sender reputation broadly.

Coordinating sales and marketing prevents exceeding the 3-contact limit. Establish clear ownership for target accounts and ensure both teams have visibility into who's receiving outreach. This coordination protects sender reputation while ensuring prospects receive consistent messaging rather than conflicting outreach from multiple people at your company.

Optimal sending timing also matters: Tuesday through Thursday, 9-11 AM in the recipient's timezone performs best for B2B. Avoid Mondays when inboxes are overloaded and Fridays when people mentally check out early.

6. Architect your sending infrastructure strategically

One architectural decision provides ongoing protection: send from subdomains rather than your root domain. This allows you to isolate sending reputation by function. If marketing email reputation suffers, your primary domain remains protected for transactional emails, website communications, and other critical messages.

Consider dedicated IP addresses once reaching substantial monthly email volume. Below that threshold, shared IPs typically deliver better results because they benefit from pooled reputation across multiple senders.

Stay on shared IPs if you're sending moderate volumes monthly or have inconsistent sending patterns. Move to dedicated IPs if you're sending consistently high volumes, need complete control over sender reputation, or want to separate marketing and transactional email entirely.

Evaluate dedicated IP strategy based on actual sending volumes across all coordinated campaigns, not just marketing emails in isolation. The decision affects your entire email program.

Subject line and content structure also impact deliverability. Keep subject lines under 50-60 characters for mobile optimization. Avoid ALL CAPS, multiple exclamation points, and spam trigger words. Maintain a balanced text-to-image ratio in email body content; never send image-only emails. Include plain text versions for all HTML emails, and use full URLs rather than URL shorteners that mask destinations.

Enhance email deliverability with Understory

Email deliverability doesn't exist in isolation. When campaigns don't reach inboxes, content promotion suffers, event follow-ups miss critical touchpoints, and product launches fail to generate pipeline. The deliverability issues compound across every campaign.

Most SaaS growth leaders face this coordination gap: no one tracks sender reputation holistically, and no one prevents teams from unknowingly triggering spam filters at key accounts through uncoordinated outreach.

At Understory, we coordinate your entire demand generation engine, including email infrastructure. We ensure authentication covers all email types, monitor Outlook performance separately, enforce the 3-contact-per-company rule across sales and marketing outreach, and maintain sender reputation through quarterly hygiene audits.

For B2B SaaS companies with $20K+ ACVs, email deliverability is the foundation enabling your entire allbound coordination to reach decision-makers.

Book an intro call to see how coordinated demand generation eliminates deliverability issues.