Mailchimp Emails Going to Spam? Start With This Deliverability Audit

You sent the campaign. You watched the send button go green. You checked your open rates an hour later and saw nothing.

Then you asked yourself: “Why are my Mailchimp emails going to spam?”

It’s a question I get at least once a month from business owners who swear their content is good, their subject lines are solid, and their offers are strong. And they’re usually right about all of that.

The problem isn’t the email. It’s the infrastructure around it.

Why Your Emails End Up in Spam

Spam filters don’t work the way most people think. They’re not reading your content and deciding if it’s annoying. They’re checking whether your email looks legitimate — whether your domain has the credentials to send on behalf of your business.

This happens before your email even lands in an inbox. The receiving mail server runs a series of checks:

• Is the sending server authorized to send from this domain?
• Has the email been tampered with in transit?
• Is the sender’s policy consistent with other bulk senders?

If any of these checks fail, your email gets flagged. Not because it’s spam. Because it looks like it could be.

And here’s the thing that surprises most people: Gmail and Yahoo now require authentication for any sender transmitting more than 5,000 messages a day. This isn’t a suggestion. It’s a requirement that went into effect in 2024.

If you’re sending bulk email without proper authentication, you’re already on borrowed time.

The Three Records That Matter

Most deliverability problems come down to three DNS records that most people have never heard of:

SPF (Sender Policy Framework)

SPF tells receiving servers which IP addresses are allowed to send email on behalf of your domain. Without it, anyone can pretend to send from your domain — which is exactly what spammers do.

When you send through Mailchimp, you need an SPF record that includes Mailchimp’s servers. If you also send from Gmail, your website contact form, and your CRM, each of those needs to be included in the record.

The common mistake: people add Mailchimp but forget about other sending sources. Every tool that sends email from your domain needs to be listed.

DKIM (DomainKeys Identified Mail)

DKIM is a digital signature on your email. When your email leaves Mailchimp’s servers, it gets signed with a private key. When it arrives at the destination, the receiving server checks the signature against your public DKIM record.

If the signature matches, it means the email wasn’t modified in transit. If it doesn’t match — or if there’s no signature at all — the email looks suspicious.

This is how spammers get caught: they intercept emails and modify the links or content. Legitimate emails have the DKIM signature that proves they haven’t been touched.

DMARC (Domain-based Message Authentication, Reporting, and Conformance)

DMARC is the enforcement layer. It tells receiving servers what to do when SPF or DKIM checks fail:

• p=none: Do nothing. Just monitor.
• p=quarantine: Send failures to spam.
• p=reject: Reject the email entirely.

Most companies start with p=none, gather data, and eventually move to p=quarantine or p=reject. The key is that DMARC also gives you reporting — you can see when someone tries to send from your domain without authorization.

The uncomfortable stat: 85.7% of domains don’t enforce DMARC protection. That means the vast majority of businesses are leaving themselves open to spoofing and deliverability problems.

What a Deliverability Audit Actually Checks

When we audit a client’s email setup, here’s what we look at:

1. Authentication records

We check if SPF, DKIM, and DMARC are set up correctly. We verify that Mailchimp’s sending domains are authorized. We look at DMARC reports to see if there are unauthorized sending attempts.

2. Domain reputation

Your sending domain has a reputation score, just like a credit score. If you’ve sent spam in the past, if you’ve had high bounce rates, if you’ve had lots of people mark you as spam — your reputation is damaged.

We check tools like Google Postmaster to see your domain’s current standing.

3. List hygiene

This is where most problems live. A list with old email addresses, bounced emails, and unengaged contacts will tank your deliverability. Mailbox providers track how many of your emails bounce and how many people mark you as spam. Bad hygiene = bad reputation.

We look at your last 90 days of sends: bounce rate, spam complaint rate, and unsubscribe rate. Each of these affects your sender score.

4. Sending patterns

Sending to your full list once a month and then nothing for four weeks is worse than consistent, smaller sends. Spam filters look for patterns. Inconsistent sending looks like spammer behavior.

5. Content signals

While authentication is the gatekeeper, content still matters. Too many links, too many images, suspicious words in subject lines — these all contribute to spam scores. Not because you’re a spammer, but because spam often has these characteristics.

The Fix Sequence

Here’s what we do when we find problems:

Week 1: Fix authentication

Set up SPF, DKIM, and DMARC if they’re missing. Verify Mailchimp’s sending domain. Check for any unauthorized sending attempts in DMARC reports.

Week 2: Clean the list

Remove hard bounces immediately — they hurt your reputation every time you send. Remove contacts who haven’t engaged in 6+ months, or move them to a re-engagement sequence with a re-confirmation email.

Week 3: Warm up cold addresses

If you’ve been having deliverability problems, your domain reputation is probably damaged. We start fresh: lower sending volume, higher engagement focus, gradual scaling back up to normal volume over 4-6 weeks.

Week 4: Monitor and adjust

Track open rates, bounce rates, and spam complaints daily. Adjust based on data. If certain segments perform better, send more to those. If certain content gets flagged, figure out why.

Why Most People Don’t Fix This

The honest answer: it’s invisible.

You don’t know your emails are going to spam unless you check. You send the campaign, you see the open rate, you wonder why it’s low — but you assume it’s the subject line or the timing.

You never check Google Postmaster. You never look at your DMARC reports. You don’t have a way to see what’s happening at the destination.

The emails that go to spam don’t come back with an error message. They just… disappear.

This is why we always start client engagements with an email deliverability audit. It’s the foundation. If your emails aren’t reaching inboxes, nothing else matters.

The Checklist

Before you send your next Mailchimp campaign, check these:

• SPF record includes all sending sources (Mailchimp, your website, other tools)
• DKIM is verified and active in Mailchimp
• DMARC is set up (at minimum p=none)
• Hard bounces are suppressed, not just marked as bounced
• No contacts on your list older than 12 months with no engagement
• You’re sending consistently, not in big irregular batches
• You’ve checked Google Postmaster for domain reputation issues

If any of these are unchecked, you’re leaving deliverability on the table. Your emails are reaching fewer people than they should — not because your content is bad, but because the infrastructure isn’t ready.

---

Want us to audit your Mailchimp setup and show you exactly what’s breaking your deliverability? Book a free audit — we’ll check your authentication, list health, and domain reputation and give you a clear action plan.