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Deliverability is the difference between cold email that works and cold email that lands in spam. It is 80% setup + discipline, 20% craft. This walks the foundation that real cold-email operators run.
Who this is forCold email operators running Instantly campaigns whose reply rates are dropping or whose accounts have ever been flagged. If your reply rate is under 1% on warm lists, deliverability is almost certainly the problem.
What you'll need
Step 1
SPF + DKIM + DMARC + MX must all pass. Verify with mxtoolbox.com. Failures = unauthenticated emails = spam folder.
For each cold-email domain, check via mxtoolbox.com:
- SPF: must include the email provider (Google: `_spf.google.com`, M365: `spf.protection.outlook.com`).
- DKIM: must be enabled in Google Workspace Admin / M365 Defender AND the corresponding TXT record published in DNS.
- DMARC: must exist. Start with `p=none`, tighten to `p=quarantine` after 30 days of clean data.
- MX: standard for your provider, no custom forwarding that breaks the chain.
Any failure = recipient providers cannot authenticate emails = direct route to spam.
Re-verify monthly. DNS changes from admins, registrar issues, or vendor updates can break authentication silently.
Step 2
Google Postmaster Tools shows your domain reputation as seen by Gmail. Sign up, verify, monitor weekly.
Sign up at postmaster.google.com.
Verify each cold-email domain (TXT record DNS verification).
Wait 7-14 days for data to populate. Then check daily/weekly:
- Domain Reputation: Bad/Low/Medium/High. Target: High.
- IP Reputation: same scale. Less important for Instantly users (you do not control IP).
- Spam Rate: must be <0.1%. Above 0.3% = serious problem.
- Authentication: SPF/DKIM/DMARC pass percentages. Target: 95%+.
For Microsoft (Outlook/Hotmail): Microsoft SNDS provides similar data but is harder to set up.
Step 3
Verify every list before upload. Remove unsubscribes, bounces, and complaints. Bounce rate over 3% = problem.
Pre-upload verification: every list goes through Instantly's built-in verifier OR NeverBounce, ZeroBounce.
Reject any lead marked as risky, invalid, or role-based (info@/sales@/support@).
During campaigns:
- Instantly auto-suppresses unsubscribes and bounces from subsequent steps. Verify this is working.
- Manually review the bounce list weekly. Hard bounces should be removed from ALL future campaigns.
Cross-suppression: build a master suppression list across all campaigns. Use Instantly's account-level suppression feature.
Step 4
Max 30-50 emails/day per sending account, ramping up over weeks. Spikes (e.g., 100/day) trigger throttling.
Each sending account has a soft daily limit based on its reputation and age.
For warmed-up accounts: cap at 30-50/day during campaigns + 10-20/day continued warmup.
For newer accounts (post-warmup but under 60 days old): cap at 20-30/day.
Spikes are dangerous. Do not jump from 30/day to 100/day in one day — recipient providers see this as bot-like.
Ramp increases gradually: +5-10 emails/day per week if reputation is healthy.
Step 5
Avoid trigger words (free, urgent, guarantee). Avoid all-caps. Avoid excessive links. Keep emails plain-text-friendly.
Spam-trigger words: free, urgent, act now, guarantee, no obligation, click here, $$$, !!!.
Avoid ALL CAPS in subject or body.
Limit links: 1 per email is ideal. 2 is OK. 3+ is spam-triggering.
Avoid HTML-heavy emails for cold outreach — use plain text. Looks more like a real human email AND fewer spam triggers.
Avoid attachments. Image embeds. Tracking pixels (use sparingly).
Run drafts through mail-tester.com for a spam-score check.
Step 6
For 200+ emails/day, distribute across 3-5 domains. Each domain limited to 100-200/day max.
High-volume cold email should never rely on one domain.
Distribute across 3-5 domains. Each domain handles 100-200/day max via its 3-5 sending accounts.
In Instantly, campaigns can be configured to use sending accounts across multiple domains in round-robin.
Benefits: if one domain is flagged, you lose 20-30% of capacity, not 100%.
Step 7
Track inbox % from warmup, open rate, bounce rate, spam rate weekly per account. Catch drops early.
Spreadsheet or simple dashboard tracking per account weekly:
- Warmup inbox % (from Instantly).
- Campaign open rate (from Instantly).
- Campaign bounce rate.
- Campaign reply rate.
- Postmaster spam rate.
Spot trends: account with declining inbox % over 4 weeks needs intervention. Account with sudden bounce-rate spike has a list quality issue.
Without weekly review, deliverability problems compound silently for 30-60 days.
Common mistakes
Skipping DNS verification
What goes wrong: Domain has SPF but missing DKIM. Every email is marked 'unauthenticated' by recipient servers. Reply rate at 30% of what it should be. You blame the copy.
How to avoid: Verify every domain at mxtoolbox.com BEFORE first campaign. Re-verify monthly. Catch DNS drift immediately.
No Google Postmaster Tools
What goes wrong: Domain reputation drops to Low. Your emails increasingly land in Gmail spam. You see open rate drop from 50% to 20% but cannot diagnose why because you have no visibility into Gmail's view.
How to avoid: Set up Postmaster Tools on day 1. Monitor weekly. Domain reputation drops 2-4 weeks before reply rate craters — gives you time to fix.
Spammy copy
What goes wrong: Email contains 'free,' 'guarantee,' 'click here,' AND an attachment. Hit spam filters at the recipient gateway. Account flagged as spammy. Domain reputation degrades.
How to avoid: Run every email template through mail-tester.com. Score 8+/10 before launching. Cut spam-trigger words and excess links.
Sending to invalid emails
What goes wrong: 10% of list is invalid. Bounce rate at 10%. Gmail and Outlook flag the sender as 'low quality.' Subsequent emails (even to valid recipients) increasingly go to spam.
How to avoid: Pre-verify every list. Target <3% bounce rate. Above 5% is account-burning territory.
No suppression list cross-referencing
What goes wrong: Lead unsubscribed from Campaign A. Three months later you upload them again in Campaign B. They report as spam. Your sender reputation takes a hit and ALL accounts suffer.
How to avoid: Build an account-level master suppression list. Cross-reference before every new campaign upload. Use Instantly's built-in suppression.
No weekly deliverability review
What goes wrong: Domain reputation degrades from High to Bad over 8 weeks. You do not notice because you do not check. Reply rate craters. Recovery takes 3-6 months.
How to avoid: Weekly 15-min deliverability dashboard review. Catch the drop at week 2-3, not week 12.
Recap
Done — what's next
How to set up an Instantly account
Read the next tutorial
Hand it off
Deliverability is 80% discipline + 20% setup. EverestX cold email specialists run weekly deliverability monitoring across every domain and account they manage. Typical $400-800/mo at $14-16/hr — recovers more in reply-rate uplift than the cost.
See specialist rates
Most common cause: domain reputation degradation. Check Google Postmaster Tools — if reputation dropped from High to Medium/Low, your emails are increasingly landing in spam. Reduce sending volume + audit copy.
3-6 months minimum. During recovery: pause all cold email on that domain, run warmup-only for 60+ days, gradually resume sending at much lower volume. Many operators abandon burned domains rather than recover.
Eventually yes, but stage it. Start with p=none for 30 days, monitor for legitimate emails being marked. Move to p=quarantine for another 30 days. Then p=reject. Skipping stages can block legitimate transactional emails.
Apple Mail Privacy Protection (MPP) loads all images automatically, inflating reported open rates. As more recipients use MPP, your 'real' open rate appears to decrease even though nothing changed. Trust reply rate over open rate.
Both work. Instantly's verifier is convenient and bundled. NeverBounce/ZeroBounce are slightly more accurate at edge cases (catch-all detection, recent bounces). For high-stakes campaigns, use both as a check.
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