How do you check your open rate first — it tells you what kind of problem you have?

Open rate below 40% is a deliverability problem. Open rate above 40% but reply rate at zero is a messaging problem. Don't try to fix copy if you have a deliverability problem — no amount of copy improvement rescues an email that doesn't reach the inbox.

How do you check Google Postmaster Tools and Microsoft SNDS?

These are the two free dashboards that show you what Gmail and Microsoft think of your sender reputation. If you're not enrolled, enroll today — reputation drift is invisible until your opens collapse, and by then you're already 1-2 weeks behind. Postmaster has 4 buckets (High / Medium / Low / Bad). If you're Low or Bad on any sending domain, pause sending immediately.

How do you check MXToolbox for blacklists?

Run mxtoolbox.com/blacklists on every sending domain and your sending IPs. There are ~30 major blacklists; the ones that matter most are Spamhaus, Spamcop, and Barracuda. Being on Spamhaus means you can't deliver to roughly 60% of business email. Getting off takes anywhere from 24 hours (if you self-request) to weeks (if the listing is justified).

How do you run a seed-list test across providers?

Use GlockApps, MailReach, or Mailtrap to send a test email to 50-100 seed addresses across Gmail, Outlook, Yahoo, and corporate domains. You get back a placement matrix: what landed in inbox vs spam vs promotions vs didn't deliver at all. This is your forward-looking signal — re-run every 24 hours during the fix.

How do you verify SPF, DKIM, and DMARC haven't silently broken?

These records can break without warning. SPF hits the 10-DNS-lookup limit when a sending platform changes their includes. DMARC alignment fails when someone adds a new sending tool that isn't on the SPF/DKIM list. Verify with mail-tester.com — you want a 10/10 score with green checks across SPF, DKIM, and DMARC on every sending domain.

How do you check your bounce rate, complaint rate, and content fingerprint?

Pull the last 30 days of sends. Bounce rate >3% means your list is stale or you're hitting spam traps. Complaint rate >0.3% means Gmail will filter you. If both metrics look fine but you're still struggling, the problem might be content fingerprinting — Gmail flags batches of identical email bodies as mass-send.

How do you execute the recovery sequence if reputation is collapsed?

If Postmaster shows Low or Bad, you can't fix it by sending more — you have to send less. Pause completely for 24 hours. Then drop volume to 5 emails/inbox/day. Only send to engaged contacts (people who replied or opened in the last 30 days). Ramp by 5 every couple of days. Reputation rebuilds slowly — typically 2-4 weeks back to Medium, longer to High.

How do you retire the domain if it's not coming back?

Sometimes a domain is too damaged to recover. Signal: Bad reputation in Postmaster for 2+ weeks despite reduced volume, sub-30% inbox placement in seed tests, opens stuck below 10%. At that point, $12 for a new domain beats months of trying to rehabilitate the old one.

What goes wrong: You try to fix this by changing the copy first?

Bad copy gives you a 1-2% reply rate, not zero. If your opens collapsed below 20%, the problem is deliverability, not copy. Fix deliverability first — any copy improvements you make in the wrong order will be invisible because the emails aren't reaching the inbox.

What goes wrong: You send more to recover?

When replies dry up, the instinct is to send more. This is exactly wrong. Volume during a reputation slump deepens the slump. Send less, send to engaged contacts only, and give Postmaster time to register the improved behavior.

What goes wrong: You ignore Microsoft SNDS because most of your contacts are Gmail?

Even if 80% of your list is Gmail, your business contacts at any company using Microsoft 365 (most of the Fortune 5000) are on Outlook. When SNDS goes red, you silently lose all your enterprise outreach. Check both dashboards every week.

What goes wrong: You use a low-quality warmup tool?

Some warmup tools share pools with spammers and can actively cause blacklisting. The cheapest tool is rarely the right one. Use Smartlead, Instantly, MailReach, or Warmup Inbox — and read recent reviews before signing up.

What goes wrong: You don't have a baseline to compare against?

If you don't know what your healthy open rate / reply rate / bounce rate looks like, you can't tell when things degrade until they've degraded badly. Record week-1 numbers as the baseline. Re-check weekly.

What goes wrong: You leave open tracking on during recovery?

Open tracking pixels (the 1x1 image embedded in your email) actively hurt deliverability and Apple Mail Privacy Protection makes the data unreliable anyway. At high volume or during recovery, turn it off. You're trading real deliverability for fake metrics.

Playbook · Deliverability rescue

Fix deliverability when emails stop landing

Your open rate dropped, your reply rate collapsed, or your sender reputation went red. Here's the diagnostic — what to check first, what to do, and what to do when a domain is too damaged to save.

Who this is for

Founders mid-crisis. Cold email was working last week and isn't this week. You need to know what broke and how to fix it.

Time to ship

Diagnosis in 2-3 hours. Recovery in 1-3 weeks depending on damage.

What you’ll do

You'll check open rate (to tell if it's deliverability vs messaging), pull up Postmaster and SNDS, run a blacklist check, run a seed-list test, verify your auth records didn't silently break, look at bounce/complaint/fingerprint metrics, run the recovery sequence if reputation is collapsed, and replace the domain if it's not coming back.

The steps

01
Check your open rate first — it tells you what kind of problem you have
First 5 min
Open rate below 40% is a deliverability problem. Open rate above 40% but reply rate at zero is a messaging problem. Don't try to fix copy if you have a deliverability problem — no amount of copy improvement rescues an email that doesn't reach the inbox.
- Healthy: open 40-65%, reply 5-10%, bounce <2%, spam complaint <0.1%.
- Open <40% = deliverability problem. Skip to step 2 below.
- Open >40% but reply <2% = messaging or list problem. Go fix the copy or the ICP, not the infrastructure.
- Note: Apple Mail Privacy Protection inflates open rates. Use opens as a rough signal, not a precise metric. Trust replies more.
↳ Reference: Postmaster Tools and SNDS
02
Check Google Postmaster Tools and Microsoft SNDS
First 30 min
These are the two free dashboards that show you what Gmail and Microsoft think of your sender reputation. If you're not enrolled, enroll today — reputation drift is invisible until your opens collapse, and by then you're already 1-2 weeks behind. Postmaster has 4 buckets (High / Medium / Low / Bad). If you're Low or Bad on any sending domain, pause sending immediately.
- Google Postmaster: postmaster.google.com. Shows domain reputation, spam rate, IP reputation, auth pass rates. Daily granularity.
- Microsoft SNDS: sendersupport.olc.protection.outlook.com. Color-coded by IP. Yellow = warning, Red = filtered. Last 30 days.
- Both require DNS verification (Postmaster) or IP ownership proof (SNDS). 20-minute setup.
- If Postmaster is in Low/Bad, do not send another email until you've completed the recovery sequence below.
↳ Reference: Postmaster Tools and SNDS reference
03
Check MXToolbox for blacklists
Hour 1 · 10 min
Run mxtoolbox.com/blacklists on every sending domain and your sending IPs. There are ~30 major blacklists; the ones that matter most are Spamhaus, Spamcop, and Barracuda. Being on Spamhaus means you can't deliver to roughly 60% of business email. Getting off takes anywhere from 24 hours (if you self-request) to weeks (if the listing is justified).
- Spamhaus blacklisting often comes from hitting spam traps — pristine email addresses that should never receive cold email. If you hit one, you bought a bad list.
- Self-request removal at the blacklist's site. Be specific about what changed (paused sending, cleaned list, reverified emails).
- If you can't get off, replace the domain. $12 is cheaper than two weeks of failed delivery.
↳ Reference: Bounce taxonomy
04
Run a seed-list test across providers
Hour 1 · 30 min
Use GlockApps, MailReach, or Mailtrap to send a test email to 50-100 seed addresses across Gmail, Outlook, Yahoo, and corporate domains. You get back a placement matrix: what landed in inbox vs spam vs promotions vs didn't deliver at all. This is your forward-looking signal — re-run every 24 hours during the fix.
- Inbox >70% across providers = healthy. 40-70% = degraded but workable. Below 40% = active crisis.
- If Gmail is 80% inbox but Outlook is 5%, your problem is Microsoft-specific. Usually SNDS or MTA-STS related.
- Seed scores move faster than Postmaster reputation. Use seed tests during recovery to confirm the fix is working before Postmaster catches up.
↳ Reference: Seed list testing methodology
05
Verify SPF, DKIM, and DMARC haven't silently broken
Hour 1-2 · 15 min
These records can break without warning. SPF hits the 10-DNS-lookup limit when a sending platform changes their includes. DMARC alignment fails when someone adds a new sending tool that isn't on the SPF/DKIM list. Verify with mail-tester.com — you want a 10/10 score with green checks across SPF, DKIM, and DMARC on every sending domain.
- SPF showing 'permerror' = you hit the 10-lookup limit. Flatten the record or remove an include.
- DKIM showing 'no key' or 'invalid signature' = a key rotation didn't deploy. Check with your mailbox provider.
- DMARC showing alignment failures = a new sender is sending without proper auth. Check your DMARC aggregate reports to find the offender.
- Common breakage: adding a second SPF record. Only one is allowed — they cancel each other out.
↳ Reference: SPF in depth
06
Check your bounce rate, complaint rate, and content fingerprint
Hour 2 · 30 min
Pull the last 30 days of sends. Bounce rate >3% means your list is stale or you're hitting spam traps. Complaint rate >0.3% means Gmail will filter you. If both metrics look fine but you're still struggling, the problem might be content fingerprinting — Gmail flags batches of identical email bodies as mass-send.
- Bounce >3%: pause, reverify the full list (MillionVerifier, NeverBounce, Kickbox), reset the suppression list, restart.
- Soft bounce >5%: usually a content problem (suspicious words, too many links, attachments) or the recipient is throttling.
- Complaint >0.3%: rewrite copy to be less aggressive. Remove sales language. Reduce send volume per recipient.
- Identical body text across 200+ emails triggers content fingerprinting. Use spintax ({Hi|Hey|Hello}, varied opening sentences) to break the pattern.
↳ Reference: Bounce taxonomy reference
07
Execute the recovery sequence if reputation is collapsed
Days 1-14 if needed
If Postmaster shows Low or Bad, you can't fix it by sending more — you have to send less. Pause completely for 24 hours. Then drop volume to 5 emails/inbox/day. Only send to engaged contacts (people who replied or opened in the last 30 days). Ramp by 5 every couple of days. Reputation rebuilds slowly — typically 2-4 weeks back to Medium, longer to High.
- Don't go to zero forever — that signals abandonment. A small volume of good mail keeps the warming pool warm.
- Recheck Postmaster every 24-48 hours. Reputation lags seed-test scores by several days.
- Turn off open tracking pixels during recovery. They actively hurt deliverability and the data is unreliable post-Apple Mail Privacy Protection.
- Restart the warmup tool on the affected mailboxes. The synthetic engagement helps re-establish baseline behavior.
↳ Reference: Warmup and reputation rebuild
08
Retire the domain if it's not coming back
If 2 weeks of recovery don't move the needle
Sometimes a domain is too damaged to recover. Signal: Bad reputation in Postmaster for 2+ weeks despite reduced volume, sub-30% inbox placement in seed tests, opens stuck below 10%. At that point, $12 for a new domain beats months of trying to rehabilitate the old one.
- Buy a new lookalike (your.io if you were using your.com).
- Move senders to the new domain. Warm from scratch — 14-21 days.
- Park the old domain (don't delete) for 90 days. You may have outstanding threads with replies routing to it.
- Going forward: always have new domains warming in the background. Rotate roughly every 90 days at scale.
↳ Reference: Why you buy separate sending domains

What goes wrong

The failure modes that catch most founders.

You try to fix this by changing the copy first
Bad copy gives you a 1-2% reply rate, not zero. If your opens collapsed below 20%, the problem is deliverability, not copy. Fix deliverability first — any copy improvements you make in the wrong order will be invisible because the emails aren't reaching the inbox.
You send more to recover
When replies dry up, the instinct is to send more. This is exactly wrong. Volume during a reputation slump deepens the slump. Send less, send to engaged contacts only, and give Postmaster time to register the improved behavior.
You ignore Microsoft SNDS because most of your contacts are Gmail
Even if 80% of your list is Gmail, your business contacts at any company using Microsoft 365 (most of the Fortune 5000) are on Outlook. When SNDS goes red, you silently lose all your enterprise outreach. Check both dashboards every week.
You use a low-quality warmup tool
Some warmup tools share pools with spammers and can actively cause blacklisting. The cheapest tool is rarely the right one. Use Smartlead, Instantly, MailReach, or Warmup Inbox — and read recent reviews before signing up.
You don't have a baseline to compare against
If you don't know what your healthy open rate / reply rate / bounce rate looks like, you can't tell when things degrade until they've degraded badly. Record week-1 numbers as the baseline. Re-check weekly.
You leave open tracking on during recovery
Open tracking pixels (the 1x1 image embedded in your email) actively hurt deliverability and Apple Mail Privacy Protection makes the data unreliable anyway. At high volume or during recovery, turn it off. You're trading real deliverability for fake metrics.

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