Your Deliverability Sucks Because You’re Ignoring Domain Reputation Monitoring

Domain reputation is a lot like being a DJ at the club. If you read the crowd and keep the vibe right (personalised, valuable emails), people stay and dance (reply). If you play the same track over and over (duplicate content) or blast the volume too high (send too much from the same domain), people leave, and the bouncers (SPs) throw you out. One bad set can ruin your reputation, and building it takes consistency and knowing your audience.

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This is where domain reputation monitoring comes in. Maybe you can’t get an absolute measurement, but when you track the right metrics, the picture becomes clear on how your domain is doing. That’s what we discuss here.

Cold Emailer vs Marketer: What’s the Difference?

If you’re a beginner, there is a good chance that you might confuse a cold emailer and a marketer. You’ll be surprised to know that the only point of commonality between the two is sending emails. Everything else, even how the email is written, has a night and day difference between the two.

We have tried every tool in the market, and there is no one correct way to track cold email, but there are signs to look for. If you are a marketer, there are certain software tools that can help you track problems at scale. However, if you are just marketing emails (PS: To a warm audience), you should not have cold email problems.

Why Do Cold Emailers Need Domain Reputation Monitoring?

As a cold emailer, your main purpose is to get replies, but to get them, you first need to land in the inbox. And what determines you getting there? Your domain reputation.

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Your domain does not come with a reputation; it is built over time through your sending behaviour, how consistent and safe, and how human your outreach looks. Sadly, most cold emailers don’t even realise that their domain reputation has taken a hit till it is too late. It is more of a preventative measure than a safety one. You’re tracking quiet signals that affect your domain reputation, and the only people who do this are serious cold emailers. That’s why domain reputation monitoring is essential for serious cold emailers.

How To Tell If Your Domain Reputation Is Bad

When you’re using similar lead lists and similar copy, your domain's reply rate becomes your baseline for health. After a certain volume, the law of large numbers kicks in. It means that you’ll start to see patterns that indicate problems.

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Here’s how to think about it:

• If you normally get a 10% reply rate, then:
  • You should expect 10 replies per 100 emails
  • If you only get 1–2 replies, something is likely wrong

• If your reply rate is closer to 1%, then:
  • You’ll need to send at least 500 emails to spot issues clearly
  • A drop from 5 replies to 0 is still a red flag

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It's not about individual emails, it's about performance over volume. Track replies per domain over time. A sudden drop from your baseline, especially if everything else stayed the same, is often a sign that a domain has ALREADY degraded. Regular domain reputation monitoring is key to preventing deliverability issues.

How to Monitor Domain Reputation (The Right Way)

There are dozens of tools that claim to measure domain reputation, but most don't track what cold emailers actually need to know. If you’re wondering how to check my domain reputation, this is what you need to know. Some give metrics that might be useful, only if you know what to look for.

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• Inbox placement tests: These tests simulate where your emails land in the inbox. Spam or primary inbox. Aerosend does this bi-weekly for its clients.

• Blacklist monitoring: Check whether your domain or IP is listed on known blacklists.
  • Spamhaus
  • Spamcop
  • Barracuda
  • SEMFRESH
• Google Postmaster: This tool shows complaint rates if you're sending high volume to Gmail users (P.S. 0.03%+ is already bad).
• Microsoft SNDS: It’s Outlook’s postmaster, try to keep spam rates below 0.5%.
• Technical checks: Validates DNS records like SPF, DKIM, DMARC. These are important for setup, but not enough to measure reputation on a day-to-day basis. ALWAYS warm up your inboxes before, during, and even after you launch your campaign.
• Engagement Rates: If your engagement suddenly drops, it probably has something to do with your domain.

The Big Problem?

None of these tools can directly tell you if your cold emails are landing in inboxes. They only detect issues after it’s already too late. If your open or reply rates are falling, it usually means your emails are going to spam, but no tool will warn you before that happens. Unfortunately, most domain reputation monitoring tools miss the early signs that matter to cold emailers.

How Do You Actually Monitor Domain Reputation?

The best indicators are right in front of you. Your own campaign metrics. You should keep an eye on:

• A consistent drop in open or reply rate across inboxes.
• Sudden bounce rate spikes (Anything more than 1% is bad).
• Spam placement during your own inbox tests.

If you're sending cold emails, reply rates are your early warning system. Once replies drop and spam rates increase, it may be time to pause that domain and rotate to a fresh one. If you want to get ahead of these issues, though, you can just use inboxes built specifically for cold emails, from Aerosend. :)

What Damages Your Domain Reputation?

While there are some things that you can’t control, there are many that you can. And you absolutely should. Listed below are some of the common mistakes that new or even experienced cold emailers can make sometimes:

Buying Bad Domains

If you got an email from apple.xyz instead of apple.com, you’re never going to respond. In fact, you would instantly think that something is fishy. Choosing shady or uncommon TLDs like .xyz, .mnc, or .top instead of reputable ones like .com or .io can instantly hurt deliverability. Spammers have abused many of these domains, and mailbox providers treat them with suspicion from day one, even before you send a single email. It’s really not worth the risk or the headache.

No Technical Setup

If email providers cannot verify you, they will not let you land in the inbox either. Your DNS records (SPF, DKIM, DMARC) need to be properly set up so that providers don’t think you’re suspicious.

No Warm Up

Would you trust a DM from an account with zero followers? Probably not. Would you reply to a verified account with 500+ followers? Perhaps. The difference between the two is that one looks more trustworthy and safer than the other. Similarly, launching cold emails from a fresh inbox with no sending history screams spam. You need to gradually build up volume and engagement first.

No Sending Strategy

It is better not to send at all instead of sending with no strategy. Inconsistent sending volumes and low-quality lists will be your biggest enemies here. These things make you look spammy. A lack of structure leads to long-term damage, if you even manage to do this long-term with a bad setup. (It’s not really possible.)

Sending Too Much from One Domain

Don’t put all your eggs in one basket. Diversify. Especially if you plan to scale up. Multiple inboxes and domains should be a no-brainer. If you're funnelling all your cold emails through a single domain, you’re putting all your reputation eggs in one basket. When you do this, even a small issue can stop your whole operation.

Spam Complaints

You can’t see who marks you as spam, but you know who does? Your email provider. Of course, it may be out of your control who marks you as spam, but you still do everything in your power so they don’t. No authentication, poor copy, bad targeting, etc, are all reasons you could end up getting a complaint.

Domain Health Checker Tools

Again, there is no absolute way to check your domain reputation; there are domain health tracking tools that can help point you in the right direction. These domain health tracking tools focus on spam rates, complaints, and blacklist data.

Google PostMaster

Most cold emailers start with Google. The postmaster tool lets you track domain reputation between Gmail accounts. You’ll be able to see colour-coded domain reputation ratings and spam rate tracking. Ideally, spam rates should always be below 0.3%.

Microsoft SNDS

Microsoft Smart Network Data Services works for Outlook. Like Postmaster, this also shows you the complaint rate (stay below 0.5% here). Additionally, you get Junk Email Reporting Program (JMRP) data, which can help you with any messaging issues. At the end, you get your sender reputation, which you would obviously want to be high.

Sender Score

This is a third-party tool that takes a bunch of things like engagement metrics, inbox placement, among others, to give a score on the scale of 0-100. It tells you how likely your domain is to trigger spam filters.

How to Automate Monitoring Into Your Cold Email Stack

Managing 10+ domains manually isn’t scalable. You need to automate what you can, when you can.

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• Integrate tools like Smartlead or Instantly into your cold email stack
• Use inboxes made for cold emailers by Aerosend
• Set up real-time alerts based on bounce rates, blacklist appearances, and inbox placement changes
• Schedule weekly health reports to track trends and act before your domains are damaged

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Bonus Tip: Aerosend sends real-time alerts on blacklist status, and we do bi-weekly inbox placement tests for all our clients.

What To Do If Domain Reputation Drops

If you suspect something’s wrong based on your domain reputation monitoring, there are steps you can take to move forward. (No, not all problems are fixable. Especially when it comes to a bad domain.)

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• Pause inboxes or rotate sending. Never continue sending from a burned inbox.
• Rest the domain for a few days or weeks (or retire it completely if it’s beyond repair).
• Create a Do Not Contact (DNC) list. These are leads that have either asked not to be contacted or the ones that you have already contacted.
• Use Spintax and refresh your copy, a little change in the copy sometimes can go a long way.
• Warm up. Always. There is no reason to stop unless you know you have to get rid of a domain entirely