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Cold Email Troubleshooting: Fix Spam, Burned Mailboxes, and Low Reply Rates
Troubleshooting
Blog > Troubleshooting
By Nikita Bykadarov, CEO of Maildoso · Updated June 15, 2026
Find Your Problem, Get the Fix
Cold email breaks in a handful of predictable ways. Mail that used to land in the inbox starts hitting spam. Mailboxes burn out. Reply rates slide for no obvious reason. Google suspends your accounts mid-campaign, or your domain quietly fails DMARC. Each one has a cause you can find and a fix you can run today.
Pick your symptom below – every guide gives you the answer first, then the steps to recover and the way to stop it happening again. Most of these problems share one root: infrastructure that was never built for cold outreach. Fix that, and the rest stops recurring.
Pick your symptom below – every guide gives you the answer first, then the steps to recover and the way to stop it happening again. Most of these problems share one root: infrastructure that was never built for cold outreach. Fix that, and the rest stops recurring.
Written by Nikita Bykadarov, CEO of Maildoso.
Nikita runs Maildoso, the cold email infrastructure platform behind 400,000+ mailboxes and 10M+ emails sent per day for 6,000+ companies. He's spent the last several years deep in the deliverability and outbound tooling space, which is why this catalog is opinionated about what actually moves reply rates — not just what's popular.
Nikita runs Maildoso, the cold email infrastructure platform behind 400,000+ mailboxes and 10M+ emails sent per day for 6,000+ companies. He's spent the last several years deep in the deliverability and outbound tooling space, which is why this catalog is opinionated about what actually moves reply rates — not just what's popular.
Start here – the four problems we get asked about most
1️⃣ Emails going to spam
Your placement collapsed and replies stopped. Find out why and how to land in the inbox again.
→ /blog/troubleshooting/emails-going-to-spam
Your placement collapsed and replies stopped. Find out why and how to land in the inbox again.
→ /blog/troubleshooting/emails-going-to-spam
2️⃣ Mailboxes got burned
Open rates near zero, bounces climbing. Learn how to tell, what you can recover, and when to rebuild.
→ /blog/troubleshooting/mailboxes-burned
Open rates near zero, bounces climbing. Learn how to tell, what you can recover, and when to rebuild.
→ /blog/troubleshooting/mailboxes-burned
3️⃣ Reply rate dropped
Same list, same copy, fewer replies. Diagnose the cause and bring your numbers back up.
→ /blog/troubleshooting/reply-rate-dropped
Same list, same copy, fewer replies. Diagnose the cause and bring your numbers back up.
→ /blog/troubleshooting/reply-rate-dropped
4️⃣ Google Workspace suspended
Your accounts got flagged mid-campaign. Here's how to respond and how to send without it happening again.
→ /blog/troubleshooting/workspace-suspended
Your accounts got flagged mid-campaign. Here's how to respond and how to send without it happening again.
→ /blog/troubleshooting/workspace-suspended
Browse by problem: Deliverability & spam
When your mail stops reaching the inbox, start here.
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Mailbox health & recovery
Burned, suspended, or flagged accounts — diagnose and recover.
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Reply rates & performance
Your sends land but nobody answers. Find the leak.
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Films are chosen in each category by a section director with the advice of a committee of film experts.
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Learn how to get there, where to stay and how to have the best time.
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Setup & integrations
Connecting mailboxes to your tools without breaking deliverability.
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Films are chosen in each category by a section director with the advice of a committee of film experts.
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Learn how to get there, where to stay and how to have the best time.
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Authentication & domains
SPF, DKIM, DMARC, and domain strategy — the technical layer that quietly kills campaigns.
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Simplicity is about subtracting the obvious and adding the meaningful.
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Films are chosen in each category by a section director with the advice of a committee of film experts.
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Learn how to get there, where to stay and how to have the best time.
Nordic nature and Scandinavian lifestyle
The ways that vast empty spaces affect how you feel and how to spend your summer the Scandinavian way.
Warmup
How to ramp new mailboxes so they don't burn on the first send.
Read more →
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Simplicity is about subtracting the obvious and adding the meaningful.
10 summer festivals from Berlin to Leipzig
Films are chosen in each category by a section director with the advice of a committee of film experts.
An urbanist's guide to the best cities to visit
Learn how to get there, where to stay and how to have the best time.
Nordic nature and Scandinavian lifestyle
The ways that vast empty spaces affect how you feel and how to spend your summer the Scandinavian way.
Scaling
Adding volume without losing the inbox.
Read more →
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Simplicity is about subtracting the obvious and adding the meaningful.
10 summer festivals from Berlin to Leipzig
Films are chosen in each category by a section director with the advice of a committee of film experts.
An urbanist's guide to the best cities to visit
Learn how to get there, where to stay and how to have the best time.
Nordic nature and Scandinavian lifestyle
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Still stuck?
Most of these problems trace back to one thing: infrastructure that wasn't built for cold email. You can keep nursing burned accounts and fighting spam filters, or you can fix the root cause.
Two ways we can help:
Book a free deliverability review
We'll look at your campaigns, run placement tests, and tell you exactly what's broken.
→ Book a demo (available only for Maildoso clients, 100% free).
Rebuild on infrastructure that won't burn
Mailboxes from $0.49 with SPF, DKIM, and DMARC auto-configured, warmup built in, and one-click connection to Instantly, Smartlead, and more.
→ See pricing
Two ways we can help:
Book a free deliverability review
We'll look at your campaigns, run placement tests, and tell you exactly what's broken.
→ Book a demo (available only for Maildoso clients, 100% free).
Rebuild on infrastructure that won't burn
Mailboxes from $0.49 with SPF, DKIM, and DMARC auto-configured, warmup built in, and one-click connection to Instantly, Smartlead, and more.
→ See pricing
FAQ
- Q:Why did my cold email stop working all of a sudden?A:A sudden drop almost always means a reputation or authentication change, not a copy problem. The usual causes: you ramped volume too fast, mailed a bad list that spiked bounces or complaints, broke SPF/DKIM/DMARC, or your domain or mailbox got flagged. Run a placement test across Gmail, Outlook, and Yahoo to confirm it's reputation, then trace it to the day it dropped and what you changed.
- Q:How do I know if it's a deliverability problem or a copy problem?A:Look at open rates and seed placement first. If your own test emails land in spam and open collapsed across the board, it's deliverability – fix infrastructure before you touch the copy. If placement is fine and opens are normal, but replies are low, it's targeting or copy. Diagnosing the wrong layer wastes weeks.
- Q:How long does it take to recover deliverability?A:Plan on two to four weeks. Reputation rebuilds slowly through warmup and low-volume sending, and pushing volume to "test" whether it's fixed just re-burns it. There's no overnight fix — the fast path is preventing the damage, not racing to undo it.
- Q:Can I fix these problems myself, or do I need to start over?A:Most are fixable in place: clean the list, fix authentication, cut volume, re-warm. You only need to rebuild when the damage is permanent – a blacklisted domain, a suspended Workspace account, or a mailbox with open rates flatlined near zero. Each guide tells you which situation you're in.
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