How to Improve Your Sending Reputation After a Bounce or Complaint Warning

What the Warning Actually Means

If you landed here from the “Sending Health” card in your dashboard, something specific happened: one of two independent metrics crossed its own threshold. This is not a general “your emails look spammy” score, and it is not a judgement about your content. It is arithmetic on your recent sends.

The two metrics, and the lines they measure against:

Two things about this table matter more than the numbers themselves.

First, the two metrics are independent. Your Account Status card reads “Warning” if either one is over its line. The Bounce Rate and Complaint Rate cards each show their own figure with their own threshold underneath. Look at which card is actually amber before you do anything — a bounce problem and a complaint problem have almost nothing in common, and the fix for one will not touch the other.

Second, “Warning” is not “Suspended”. A warning means your rate is above the level where mailbox providers start paying attention, but sending still works. You have room to fix it. That room is the entire point of the warning existing — the alternative would be finding out when your sending stops.

One more mechanical detail that changes how you should respond: both rates are computed over a rolling window of your recent sending, not over your account’s lifetime. That cuts both ways. A single bad campaign can move your rate sharply, because the window is not big enough to absorb it. And equally, once you stop the bad sending, the bad sends age out of the window on their own.

The First Hour: Stop Adding to the Numerator

Before diagnosing anything, stop the sending that is still in flight. In order:

1. Pause anything scheduled. Check your campaign list for anything queued or scheduled to go out in the next day.
2. Pause automations that target the same audience. A workflow that keeps enrolling contacts from the list that caused the problem will keep feeding it.
3. Do not send a “test” campaign to see if it recovered. This is the single most common instinct and it is the wrong one.

That third point deserves an explanation, because there is a version of it that is genuinely correct and it is easy to conflate the two.

A rate is a ratio. It is tempting to reason that sending more good email grows the denominator and drags the percentage down. That is true — eventually, and only if the new sending is genuinely clean. If you have not yet found the source, “send more to dilute it” means sending to the same list that caused the problem, which grows the numerator at least as fast. You do not dilute your way out of a list-quality problem. You fix the list, then send.

Find the Send That Caused It

Account-level rates tell you that something is wrong. They almost never tell you what. For that, go campaign by campaign.

Open your campaign analytics and compare the bounce and complaint counts per campaign, not the account average. In nearly every case, the pattern is not a gradual drift across all your sending. It is one campaign, sitting far outside the rest.

Once you have found it, the useful questions are all about where its recipients came from:

• Where did this list originate? A CSV export from another platform, a CRM sync, a trade-show scan, a purchased or rented list, a scrape.
• When was it last emailed? A list that has been sitting untouched for 12 months is not the list you built. Email addresses decay at roughly 20–25% per year.
• Did those people ask to hear from you, in a form they would recognise? “They’re our customers” and “they opted in to marketing email” are different statements.
• Was it a first send to a newly imported segment? First sends to a fresh import are where both metrics go wrong most often, because it is the first time the list has ever been tested against reality.

If the outlier campaign went to a list that is old, imported, or inherited, you have your answer and you can skip straight to the relevant section below.

If It’s Your Bounce Rate

A high bounce rate is a list quality problem. It is almost never a content problem, an authentication problem, or a sending-infrastructure problem. The receiving server is telling you the address does not exist.

What to do, in order:

Stop mailing the offending list entirely. Not a smaller segment of it — all of it, until it has been cleaned. Every additional send to dead addresses adds to the numerator with no upside.

Do not re-import the same file. Bounced addresses are suppressed automatically once they have bounced, so they will not be mailed again. But a file full of addresses that have not yet been tried is not covered by that — the platform can only suppress what it has already seen fail. Re-uploading the original CSV to “make sure everyone got it” re-introduces every untested bad address in it.

Run the list through verification before it goes anywhere near a campaign. A verification service checks syntax, domain validity, and mailbox existence without sending anything. For a list you inherited or have not mailed in over a year, this is not optional — it is the difference between a 0.4% bounce rate and a 5% one.

Check for an import mistake. A surprising share of sudden bounce spikes are mechanical: a column offset in a CSV that put phone numbers in the email field, a double import, a sync that pulled in unqualified leads alongside customers. Look at a sample of the actual bounced addresses. If they look malformed rather than merely dead, the problem is the import, not the audience.

The bounce management guide covers hard versus soft bounces and how automated suppression works in detail; email list hygiene covers the cleaning cadence that keeps this from recurring.

If It’s Your Complaint Rate

A high complaint rate is a consent and expectation problem. The address was real, the email arrived, and a human being read the sender name, decided they did not want this, and pressed the spam button rather than unsubscribe.

Start with the scale, because it is easy to misjudge. The 0.1% warning threshold is one complaint per thousand delivered emails. On a 5,000-recipient send, that is five people. Five annoyed recipients is not a crisis of your business — but it is a real signal, and mailbox providers weigh complaints far more heavily than bounces precisely because a human took a deliberate action.

The causes, roughly in order of how often they turn out to be the answer:

They do not remember signing up. Usually because the sign-up was implicit — a checkout, a download, a webinar registration, an imported CRM list — and the first marketing email arrived weeks or months later, from a sender name that does not obviously match the thing they gave their address to. Nothing about the email is wrong; the recipient simply does not recognise it.

Unsubscribing was not the obvious option. Your emails carry one-click unsubscribe headers automatically, which lets the mail client show its own unsubscribe control — but plenty of recipients never see that and go looking in the email body. If your unsubscribe link is small, grey, and at the bottom of a long footer, the spam button is genuinely easier. Making it obvious does not cost you subscribers you would have kept.

The frequency changed. Someone who signed up for a monthly newsletter and started receiving three emails a week did not consent to that, from their point of view.

The list was reactivated. Mailing a segment that has not heard from you in six months or more is the highest-complaint action available. To that recipient it is indistinguishable from a list purchase.

The fixes follow directly:

• Send a re-permission email before reactivating a dormant segment — one email asking whether they still want to hear from you, and mail only the people who say yes. You will lose most of the list on paper. You had already lost it in practice.
• Make the sender name match the sign-up context. If they subscribed on a product page, the product name should be in the From line.
• Put an unsubscribe link where a mildly irritated person will find it in two seconds.
• Turn on double opt-in for your sign-up forms. A confirmation email means every future recipient has actively agreed twice, which drives both complaints and bounces down at the source.
• Stop mailing anyone who has not opened anything in six months. They will not convert, and they are your most likely complainants.

Getting Back to Healthy

Two things move your rate back down: time and clean volume. That is the whole mechanism.

Because the window is rolling, the sends that caused the problem age out of it as newer sending replaces them. You do not need to do anything for that to happen — you only need to not repeat it. How fast it happens depends entirely on how much you send. A sender doing 50,000 emails a month clears a bad campaign out of the window in days. A sender doing 2,000 a month may be looking at several weeks, because it takes that long to accumulate enough new sending to displace the old.

While you wait, the right posture is small and clean rather than paused entirely:

1. Fix the actual source first — cleaned list, re-permissioned segment, corrected import.
2. Resume with your most engaged recipients only: people who opened or clicked something in the last 30–90 days. Their bounce and complaint rates are close to zero, which is exactly what you want entering the window.
3. Watch the Sending Health card after each send rather than at the end of the month.
4. Widen the audience gradually as the numbers come down.

If your sending is already suspended, the path is different: contact support rather than waiting it out. Come with the diagnosis — which campaign caused it, where the list came from, and what you have changed. A suspension is reversible, and an account that arrives with an explanation and a fix is a straightforward conversation.

Staying Out of the Warning Zone

Most warnings are preventable with a small number of habits, none of which are expensive:

The single highest-value item on that list is the second one. Almost every reputation incident traces back to a first send to an untested audience at full volume. Sending to 500 first costs you a day and tells you everything.

For the underlying mechanics — SPF, DKIM, DMARC, warm-up, and what actually determines inbox placement — the email deliverability guide is the deeper reference. This article is the reactive half; that one is the preventive half.

Brixus365 suppresses hard-bounced addresses and complainants automatically across every campaign, sends one-click unsubscribe headers on every message, and shows both rates against their thresholds on your dashboard. Start free — 9,000 emails a month, no card.

Frequently Asked Questions