If your cold emails aren’t landing in the inbox, your copy and offer won’t get a chance to work. Deliverability is the foundation: it determines whether prospects even see your message. This guide teaches the two biggest levers you control, domain reputation (how mailbox providers judge your sending behavior) and domain authentication (how you prove you’re the real sender), so you can scale outreach without burning your domain.
Why This Matters
Deliverability problems usually don’t fail loudly, they fail silently. Instead of obvious “bounces,” you get low open rates, fewer replies, and “ghosting” that looks like a targeting or messaging issue. Strong reputation and authentication protect your pipeline by keeping your outbound predictable, measurable, and scalable. Without them, increasing volume often makes results worse.
Core Principles / Mindset
Principle 1: Inbox placement is earned over time
Mailbox providers reward consistent, responsible sending. Sudden spikes, sloppy lists, and high complaints signal “risk,” even if your intent is legitimate. Think in weeks, not days—especially when ramping volume.
Principle 2: Reputation is about behavior, not tools
Tools can help you send and track, but your list quality, content hygiene, and sending patterns determine outcomes. If your data is weak, no deliverability “hack” will hold.
Principle 3: Authentication is your proof of identity
SPF and DKIM help providers verify that your emails are legitimately sent by you. Authentication doesn’t guarantee inbox placement by itself, but it removes a major trust barrier and reduces spoofing risk.
Principle 4: Complaints and bounces are reputation killers
Spam complaints tell providers “people don’t want this.” Bounces tell providers “this sender’s data is unreliable.” Both reduce trust quickly, and recovery can take time.
Key Techniques / Strategic Approaches
Technique 1: Keep your sending volume consistent
When to use: Any time you’re running outbound, especially while scaling.
How it works: Send in steady daily/weekly patterns instead of bursts. Ramp up gradually so providers see stable behavior.
Why it works: Spammers tend to spike volume. Consistency signals controlled, legitimate sending.
Real example: Instead of sending 2,000 emails on Monday and 0 the rest of the week, send ~400/day across five business days.
Technique 2: Protect your list quality to reduce bounces
When to use: Before every campaign launch and when changing lead sources.
How it works: Verify addresses, remove invalid domains, and avoid role-based emails when possible (e.g., info@, support@) if they perform poorly for your niche.
Why it works: High bounce rates are a strong signal of careless acquisition, which lowers your domain trust.
Real example: If a list vendor adds 10–15% invalid emails, your deliverability drops fast, cleaning the list first prevents reputation damage.
Technique 3: Use “clean” email formatting and avoid spam signals
When to use: Every time you create or update templates.
How it works: Keep HTML simple, avoid heavy formatting, and write like a human. Don’t rely on image-only emails or overly promotional layouts.
Why it works: Poorly coded HTML and “spammy” patterns correlate with unwanted email, increasing filtering risk.
Real example: A short, plain-text style email with a clear question often outperforms a designed newsletter-style template in cold outreach.
Technique 4: Minimize complaints with easy opt-out and relevance
When to use: Always, especially at higher volume.
How it works: Make opting out frictionless and keep targeting tight so recipients feel the email is meant for them.
Why it works: If “unsubscribe” is hard to find, people hit “Report spam,” which damages reputation much more.
Real example: Add a simple line like “If this isn’t relevant, tell me and I’ll stop” or include a clear unsubscribe link in the footer.
Technique 5: Authenticate your domain (SPF & DKIM)
When to use: Before sending any meaningful volume from a domain.
How it works: Publish SPF and DKIM records in your DNS so mailbox providers can verify authorized sending and message integrity.
Why it works: Authentication increases trust and reduces the chance your domain is used for spoofing—both support better inbox placement over time.
Real example: When SPF/DKIM are missing, providers may treat your emails as suspicious even if the copy is great and the list is clean.
Common Scenarios & How to Handle Them
Scenario 1: “Our open rates suddenly dropped”
What’s happening: You may have triggered filtering due to a volume spike, higher complaints, or list quality changes.
How to respond: Reduce volume temporarily, tighten targeting, and remove risky segments (old leads, unverified data). Review recent changes (new list source, new template, increased sends).
Script (internal checklist): “What changed in the last 7 days, volume, list source, copy, or sending domain?”
Scenario 2: “We’re seeing a lot of bounces”
What’s happening: Your data quality is poor or you’re hitting invalid/blocked addresses.
How to respond: Pause the worst-performing segment, verify new leads, and stop sending to addresses that bounce. Only scale once bounce rate is controlled.
Rule of thumb: Treat bounces as a data problem first, not a copy problem.
Scenario 3: “We got blacklisted”
What’s happening: A blacklist provider flagged your domain based on complaint/bounce patterns or suspicious activity.
How to respond: Identify the blacklist(s), follow their delisting process, and fix the root cause (list quality, volume spikes, missing opt-out). Expect delisting to take time.
Operational approach: Document what caused it so you don’t repeat the same pattern on a new domain.
What NOT to Do / Common Mistakes
Mistake: Sending big volume bursts.
Why it backfires: Looks like spam behavior and triggers filters.
Do this instead: Ramp gradually and keep daily volume steady.Mistake: Emailing unverified or purchased lists without cleaning.
Why it backfires: Bounces rise, reputation drops.
Do this instead: Verify and remove risky segments before launch.Mistake: Over-designed, messy HTML templates.
Why it backfires: Can trip spam filters and reduce readability.
Do this instead: Use simple formatting and human-sounding copy.Mistake: Hiding or omitting opt-out.
Why it backfires: Prospects report spam instead of unsubscribing.
Do this instead: Make opt-out obvious and easy.Mistake: Skipping SPF/DKIM setup.
Why it backfires: Providers can’t reliably trust your sender identity.
Do this instead: Authenticate before scaling outbound.
Practice This / Skill Development
Exercise 1: Reputation hygiene review (weekly)
Every week, review bounce rate, complaint signals (if available), and open/reply trends. Write down one hypothesis for any sudden change (list source, volume, copy, segment).Exercise 2: List-quality gate (before every campaign)
Create a pre-launch checklist: verified emails only, remove past hard-bounces, exclude very old leads unless re-verified.Exercise 3: Template simplification drill
Take your most “designed” email and rewrite it as a short, plain-text style message. Compare performance over a small test before rolling out broadly.
How lemlist Enables This
Consistent sending at scale: Automation helps you maintain steady sending patterns instead of manual bursts.
Personalization to reduce complaints: Better relevance usually means fewer spam reports and more replies.
Performance tracking: Monitoring campaign metrics helps you spot deliverability issues early (before they tank results).
Measuring Success
Stable open rates (directionally consistent): Sudden drops often indicate filtering or list problems.
Low bounce rate: A key indicator that your data and targeting are healthy.
Reply quality stays strong as volume increases: If replies get worse as you scale, you may be expanding into less relevant segments (which can increase complaints).
Real Examples
Example 1: Volume spike caused inboxing issues
Situation: A team increased sending from 200/day to 1,200/day overnight on the same domain.
Approach: They reduced volume, rebuilt consistency over 2–3 weeks, and tightened targeting to their highest-fit ICP segment.
Outcome: Open/reply rates recovered once sending stabilized and complaints decreased.
Example 2: Authentication improved trust signals
Situation: A new outbound domain had decent targeting but inconsistent inbox placement.
Approach: They set up SPF and DKIM, then kept volume steady while refining copy.
Outcome: Deliverability became more consistent, making campaign testing more reliable.
Quick Reference / Cheat Sheet
Reputation = behavior: consistent volume, low bounces, low complaints, clean formatting.
Authentication = identity: set up SPF + DKIM before scaling.
If metrics drop suddenly: check recent changes (volume, list source, template), then reduce volume and clean segments.
Always include opt-out: fewer spam complaints, better long-term sending health.
Advanced (Optional): Pre-empt deliverability risk when scaling
Before increasing volume, run a controlled test on a small segment and keep everything else constant (same list source, same template structure, same sending schedule). If performance holds steady, scale in steps, not leaps. Treat deliverability like sales process: predictable inputs create predictable outputs.