---
title: "Bounces, complaints and list hygiene | Optimize All Academy"
description: "Reputation is earned per send Mailbox providers watch how recipients react to your email. Signals that hurt reputation include bounces, spam complaints…"
url: https://optimizeall.com/learn/email-marketing-and-automation/list-hygiene-bounces-complaints
updated: 2026-10-05
---

Email Marketing & Automation · Deliverability · lesson 5 of 16 · 15 min

# Bounces, complaints and list hygiene

## Reputation is earned per send

Mailbox providers watch how recipients react to your email. Signals that hurt reputation include **bounces, spam complaints, spam trap hits and low engagement**. Signals that help include opens (where measurable), clicks, replies, moving emails out of spam and adding you to contacts. List hygiene is the routine work that keeps these signals healthy.

## Bounces

A **bounce** is an email that could not be delivered.

- **Hard bounce:** permanent failure – the address does not exist or the domain is invalid. Remove hard-bounced addresses immediately (most platforms suppress them automatically).
- **Soft bounce:** temporary failure – mailbox full, server busy, message too large. Platforms usually retry; repeated soft bounces over several sends should be suppressed.

A high bounce rate usually means old, purchased or mistyped data. Common causes include typos at sign-up (for example "gmial.com"). Real-time email validation at the form and double opt-in reduce them.

## Spam complaints

A complaint happens when a recipient clicks "Report spam". Complaints are one of the strongest negative signals. Common causes:

- People do not remember signing up (long gaps between sign-up and first email).
- Emails are too frequent or not what was promised.
- The unsubscribe link is hard to find, so "Report spam" is easier.
- The list includes people who never consented.

To reduce complaints:

- Send a welcome email immediately after sign-up.
- Make the sender name recognisable and consistent.
- Keep frequency aligned with what you promised.
- Put a clear unsubscribe link in every email and support one-click unsubscribe.
- Sign up to **feedback loops** where available (your email platform typically handles these) so complainers are suppressed automatically.

## Spam traps

**Spam traps** are addresses used by mailbox providers and anti-spam organisations to catch poor practices.

- **Pristine traps:** addresses never used by a real person – they appear on scraped or purchased lists.
- **Recycled traps:** old abandoned addresses reactivated as traps – they catch senders who never remove inactive subscribers.
- **Typo traps:** common misspellings of real domains.

Hitting traps can cause blocklisting. The cure is prevention: consent-based collection, validation and regular removal of long-term inactive addresses.

## Engagement-based sunsetting

Subscribers who have not engaged for a long time drag down reputation. A **sunset policy** handles them:

1. Define inactivity (for example no clicks in 6 months and no purchases in 12 months – choose thresholds that fit your sending frequency and sales cycle).
2. Send a **re-engagement** sequence (covered in the automation module) asking if they still want to hear from you.
3. Suppress those who still do not engage. They can resubscribe any time.

A smaller, engaged list almost always outperforms a large, unengaged one in both inbox placement and revenue per email.

## Monitoring dashboard

| Metric | What to watch |
|---|---|
| Hard bounce rate | Should be very low; spikes point to bad data sources |
| Spam complaint rate | Keep below 0.1% (Gmail); never approach 0.3%; investigate any spike immediately |
| Unsubscribe rate | Rising rates suggest frequency or relevance problems |
| Click rate by segment | Declining engagement predicts deliverability problems |
| Google Postmaster Tools | Spam rate, domain reputation and authentication at Gmail |
| Blocklist checks | Occasional checks with a reputable blocklist lookup |

## Content factors (smaller but real)

- Avoid misleading subject lines and excessive capitals or symbols.
- Keep a healthy text-to-image balance; image-only emails are harder to read and filter.
- Use reputable link destinations and avoid URL shorteners known for abuse.
- Include a plain-text version (most platforms generate one).

## Worked example (illustrative)

A US-based creator's list of 40,000 has a 0.4% complaint rate and falling Gmail placement. Investigation: 15,000 subscribers came from a giveaway three years ago and have not clicked in over a year. She sends a three-email re-engagement series, suppresses about 11,000 who do not respond, moves weekly emails to a clear schedule and adds one-click unsubscribe. Complaint rates fall below 0.1% and click rates per email rise.

## Common mistakes

- Keeping hard bounces on the list.
- Never removing inactive subscribers.
- Hiding the unsubscribe link.
- Long gaps between sign-up and first email.

## Reading bounce codes

Bounce messages include SMTP status codes. A few you will see often:

| Code (example) | Meaning | Action |
|---|---|---|
| `5.1.1` | Mailbox does not exist | Hard bounce – suppress immediately |
| `5.7.x` (for example `5.7.26`, `5.7.515`) | Rejected for policy or authentication reasons | Fix SPF/DKIM/DMARC or content policy; do not simply retry |
| `4.2.2` | Mailbox full | Soft bounce – retry; suppress after repeated failures |
| `4.7.x` | Temporarily deferred (rate limiting, reputation) | Slow down, check reputation and engagement |

Codes starting with **5** are permanent; **4** are temporary. Your email platform classifies most of them automatically – but a sudden wave of `5.7.x` rejections is an authentication or reputation emergency, not a list problem.

## Hands-on: a sunset policy and re-engagement series

**Policy (adapt thresholds to your send frequency and buying cycle):**

```text
Inactive = received >= 8 emails AND no clicks in 180 days AND no orders in 365 days
           AND subscribed > 90 days ago
Step 1: remove from regular campaigns; enter 3-email re-engagement flow
Step 2: anyone who clicks -> back to "engaged"; offer preference centre
Step 3: no click after final email + 7 days -> suppress (do not delete consent record)
Review: monthly; report number sunset and any change in spam rate / placement
```

**Re-engagement copy:**

```text
Email 1  Subject: Still want to hear from us?
         Body: It's been a while. We don't want to crowd your inbox. Here's what's
         new [3 bullets]. Want to keep getting our emails? [Yes, keep me subscribed]
Email 2  Subject: Pick what you'd like (or less often)
         Body: Choose topics or switch to a monthly digest. [Update my preferences]
Email 3  Subject: We'll stop emailing you soon
         Body: Unless you click below, this is our last email. No hard feelings –
         you can re-subscribe anytime. [Keep me on the list]
```

No guilt-tripping, no fake urgency, and a clear unsubscribe link in every email.

## Feedback loops and monitoring tools

- **Google Postmaster Tools:** spam rate, authentication and delivery errors for Gmail.
- **Yahoo Sender Hub:** sender information and Yahoo's complaint feedback loop.
- **Microsoft SNDS and JMRP:** data and complaint reports for Outlook.com traffic.

Most email platforms process feedback-loop complaints automatically by suppressing the complainer; confirm yours does.

## Worked example 2: a Pakistani e-commerce brand after a sale season

After an 11.11 and White Friday push, a Karachi store sees Gmail spam rate rise to 0.2% and more `4.7.x` deferrals. Investigation: sends to the whole list three times a day, including 70,000 addresses from an old contest. Fixes: frequency caps (one promotional email a day maximum), segment-based sending, the sunset policy above and a pause on the contest segment pending re-engagement. Deferrals clear and spam rate returns below 0.1% within weeks.

## Video lecture: List hygiene: bounces, complaints and knowing when to let go

Lecture coming soon · 11 chapters · about 8 minutes. Read the full transcript below.

1. List hygiene
2. Reputation signals
3. Bounces
4. Complaints
5. Spam traps
6. Sunset policy
7. Re-engagement copy
8. Example 1: US creator (illustrative)
9. Example 2: Karachi store (illustrative)
10. Monitoring
11. Recap and try this now

## Lecture transcript

### List hygiene

Here's a counter-intuitive truth about email. Sometimes the fastest way to make more money is to email fewer people. That sounds wrong, until you understand that mailbox providers judge you on how your whole list reacts. Thousands of people who never open, never click and sometimes hit report spam drag down the chances that your best customers see your email at all. In this lecture you'll learn how bounces, complaints and spam traps affect your reputation, how to read bounce codes, how to run a sunset policy with a re-engagement series, and which monitoring tools to check.

### Reputation signals

Reputation is earned send by send. Signals that hurt include bounces, spam complaints, spam trap hits and low engagement. Signals that help include clicks, replies, people moving your email out of spam and adding you to their contacts. Think of it like a restaurant review site. A few bad reviews among hundreds of good ones barely matter. But if most diners just walk out without eating, the site notices. List hygiene is the routine work that keeps these signals healthy, and it's far cheaper than trying to repair a damaged reputation later.

### Bounces

Let's start with bounces, emails that couldn't be delivered. A hard bounce is permanent: the address doesn't exist, or the domain is invalid. Remove it immediately, and most platforms do this automatically. A soft bounce is temporary: mailbox full, server busy, message too large. Platforms retry, and you suppress after repeated failures. Bounce messages include codes. Codes starting with five are permanent; codes starting with four are temporary. Five point one point one means the mailbox doesn't exist. But watch for five point seven codes, which mean rejected for policy or authentication reasons. A sudden wave of those is an emergency, not a list problem.

### Complaints

Next, complaints: when someone clicks report spam. It's one of the strongest negative signals there is. Why do people complain? They don't remember signing up, often because of a long gap before the first email. Emails are too frequent or not what was promised. The unsubscribe link is hard to find, so report spam is easier. Or they never consented at all. So send a welcome email immediately, use a recognisable sender name, keep to the frequency you promised, and make unsubscribing effortless with one-click unsubscribe. And make sure complaints from feedback loops automatically suppress the person.

### Spam traps

Now spam traps: addresses used by mailbox providers and anti-spam organisations to catch poor practices. Pristine traps were never used by a real person, so they only appear on scraped or purchased lists. Recycled traps are old, abandoned addresses reactivated as traps, catching senders who never remove inactive subscribers. And typo traps are common misspellings of real domains, like gmial dot com. Hitting traps can get you blocklisted. The cure is prevention: consent-based collection, real-time validation at sign-up, double opt-in, and regular removal of long-term inactive addresses.

### Sunset policy

That brings us to the sunset policy. Define inactivity based on your sending frequency and buying cycle. For example: received at least eight emails, no clicks in a hundred and eighty days, no orders in a year, and subscribed more than ninety days ago. Remove those people from regular campaigns and send a three-email re-engagement series. Anyone who clicks goes back to engaged, with a preference centre offer. Anyone who doesn't, a week after the final email, gets suppressed. Suppressed, not deleted, so you keep the consent record. The full policy and email copy are in the lesson text. Here's the key idea. A smaller, engaged list almost always outperforms a large, unengaged one.

### Re-engagement copy

Let's hear the re-engagement copy, because tone matters. Email one: still want to hear from us? It's been a while, we don't want to crowd your inbox, here's what's new, and a button saying yes, keep me subscribed. Email two: pick what you'd like, or less often, with topic choices and a monthly digest option. Email three: we'll stop emailing you soon. Unless you click below, this is our last email. No hard feelings, you can re-subscribe any time. Notice what's missing. No guilt-tripping, no fake urgency, and a clear unsubscribe link in every one.

### Example 1: US creator (illustrative)

Let's do a simple worked example with illustrative numbers. A US-based creator has a list of forty thousand, a complaint rate around zero point four percent, and falling Gmail placement. Investigation: fifteen thousand subscribers came from a giveaway three years ago and haven't clicked in over a year. She sends the three-email re-engagement series, suppresses about eleven thousand who don't respond, moves her weekly email to a clear, consistent schedule, and adds one-click unsubscribe. Complaint rates fall below zero point one percent, and clicks per email actually rise, with a smaller list.

### Example 2: Karachi store (illustrative)

Now a realistic scenario after a sale season. After an eleven eleven and White Friday push, a Karachi store sees its Gmail spam rate climb to zero point two percent, plus more four point seven deferrals, which means Gmail is slowing them down. The cause: sending to the whole list three times a day, including seventy thousand addresses from an old contest. The fixes: a frequency cap of one promotional email a day, segment-based sending, the sunset policy, and a pause on the contest segment until it's re-engaged. Within weeks, deferrals clear and the spam rate falls back below zero point one.

### Monitoring

Which tools should you check? Google Postmaster Tools shows your spam rate, authentication and delivery errors at Gmail. Yahoo Sender Hub covers Yahoo, including its complaint feedback loop. And Microsoft's SNDS and JMRP cover Outlook dot com. Most email platforms process feedback-loop complaints automatically, so confirm yours does. Also watch hard bounce rate, which should be very low, unsubscribe rate, and click rate by segment, because declining engagement predicts deliverability problems before they hit. Common mistakes: keeping hard bounces, never removing inactives, hiding the unsubscribe link and long gaps between sign-up and the first email.

### Recap and try this now

Let's recap. Bounces, complaints, spam traps and low engagement damage your sender reputation; clicks, replies and not-spam actions help. Remove hard bounces immediately, suppress repeated soft bounces, and treat five point seven rejections as an authentication emergency. Prevent complaints with instant welcomes, promised frequency and easy unsubscribes. And run a sunset policy with a respectful re-engagement series. Here's your try this now. Pull your bounce, complaint and unsubscribe rates for your last five campaigns, then adapt the sunset policy in the lesson text with thresholds that fit your sending frequency.

## Key takeaways

- Bounces, complaints, spam traps and low engagement damage sender reputation; clicks and replies help.
- Remove hard bounces immediately and suppress repeated soft bounces; validate addresses at sign-up.
- Prevent complaints with prompt welcome emails, promised frequency, recognisable sender names and easy unsubscribes.
- Use a sunset policy with re-engagement to keep the list smaller but healthier.

## Try it

Pull your list's (or a sample list's) bounce, complaint and unsubscribe rates for the last five campaigns and write a sunset policy with specific inactivity thresholds.

- [Previous: Google, Yahoo and Microsoft sender rules, one-click unsubscribe and BIMI](https://optimizeall.com/learn/email-marketing-and-automation/bulk-sender-requirements-and-bimi)
- [Next: Apple Mail Privacy Protection, inbox tabs and AI-powered inboxes](https://optimizeall.com/learn/email-marketing-and-automation/inbox-privacy-and-modern-inboxes)
- [All lessons of Email Marketing & Automation](https://optimizeall.com/learn/email-marketing-and-automation)