Any legitimate sender or well-meaning email marketer would take offense if their emails start getting sorted into spam folders.
Totally fair. It kind of feels like getting backstabbed. You have the subscriber permission, you’re not blasting strangers, and your content isn’t malicious.
Yet, spam complaint rates shoot up and your email deliverability and sender reputation south.
The worst thing is that you might be doing it all “right” (you think) and still end up in the spam folder.
But instead of getting defensive (been there), it’s smarter to figure out what’s triggering these spam complaints. Because you can’t stop a problem until you spot it.
In this blog, we’ll unpack the reasons behind the palpable uptick in your spam complaint rates.
Quick Primer: What Is a Spam Complaint—and Why Does It Matter?
In Email Mavlers’ latest infographic, “Email Marketing Trends and Insights, 2025”, the resounding trend that most email marketing experts advise to point your gaze on is email deliverability. But to maintain strong deliverability, you must avoid trouble with spam complaints.
Spam. The word itself already sounds sus. Perhaps it’s no coincidence it rhymes with scam. Something that a legitimate, permission-based marketer would never do.
What is spam, really?
Back in the day, spam meant emails you didn’t sign up for. Like those random discounts, shady offers, and badly photoshopped images. But that’s no longer the whole picture.
As email marketing expert Chad S. White puts it in his book Email Marketing Rules:
“Having permission only gets you so far nowadays. These days, both users and inbox providers see spam as any email that feels unwanted or irrelevant.”
Translation: Even if a user opt-in to receive your emails, if they feel emails are irrelevant, unexpected, or annoying, they can report them as spam.
And they do. Often.
So, what exactly is a spam complaint?
A spam complaint happens when a subscriber on your email contact list clicks the “Report Spam” or “Junk” button in their inbox. It reports to the mailbox providers that your email was unwanted.
It’s worse than unsubscribing. Unsubscribes are a clean break. Spam complaints are messy. Damaging? Yes, that, too.
When enough people mark your email as spam, it sends a message to Gmail, Yahoo, Outlook, and friends that your email content might be a threat to the inbox experience. Which means…
Why Spam Complaints Hurt Your Deliverability
A higher spam complaint rate nibbles away at your sender reputation. Sender reputation score (along with other factors) is what forms the basis of how credible you appear as a sender to the inbox providers.
Jaina Mistry, an expert from Litmus, has a valid point here. She says:
“At the end of the day, it’s your subscribers and inbox providers who decide what counts as spam, not you.”
So if the recipient thinks your email is spam—even if you had their permission—guess what? It is.
Mailbox providers look at your spam complaint rate, which is the percentage of your recipients who report your email as spam. Google and Yahoo’s new sender requirements set the spam rate threshold at 0.3%. However, most platforms consider anything above 0.1% (i.e., 1 in 1,000 people) to be an unsafe territory.
That’s because most inbox providers, Gmail particularly, do not share detailed spam complaint data with email service providers (ESPs) to protect it from spammers.
So the spam complaint rate shown in your email platform might actually be lower than what inbox providers are seeing. Especially if a large portion of your audience uses Gmail. Given this anomaly, it’s recommended to stay under 0.1%.
The problem starts when you consistently exceed this benchmark. Over time, your emails might start:
- Skipping the inbox and going straight to spam.
- Getting throttled (delivered slowly or inconsistently).
- Or being blocked altogether.
And you wouldn’t be wrong to think that with fewer emails reaching subscribers, your open rates decrease, click-through rates lower, and revenue from email overall suffers.
Why Do Spam Complaints Occur?
Cause #1: Inaccurate or Unclear Sender Information
A big reason subscribers mark emails as spam is because they don’t know who it’s from.
One of the easiest ways that this happens is by messing up the sender information. And we don’t mean intentionally misleading anyone. Even well-meaning senders get tripped up here.
The CAN-SPAM Act requires that your ‘From,’ ‘To,’ ‘Reply-To,’ and other email details, such as your domain and email address, must clearly show your sender identity and not be misleading.
Meaning, they must identify who sent the message and not mislead the recipient in any way.
This email got it right.
Here, the sender is listed as “Roxanne at Canto.” It’s clear who the email is from—a person at a known company. Even if the subscriber doesn’t remember Roxanne specifically, Canto adds brand recognition. This kind of clarity builds trust and reduces the likelihood of emails being overlooked in the inbox.
Which this email is failing to do.
I have picked this email from my spam folder. The sender is listed as sara…@techtargetdata.s…, which gives no real name, no brand, and zero context. Confusion = complaint. Or, in this case, the inbox filters made the call before the user even got a chance to.
Cause #2: Sending Frequency Issues
Sending emails too frequently is another mistake marketers often make without realizing it’s detrimental to their email deliverability.
A simple rationale would be more emails = more engagement until you know it doesn’t work that way. For many subscribers, it simply creates fatigue, even if the content is of high quality. And instead of unsubscribing, many take the faster route: they report emails as spam. Inbox providers monitor this, and more emails go to spam—even for your engaged subscribers.
Even brands with solid content and permission get caught in this trap. Especially during seasonal campaigns or back-to-back promos.
That’s how one simple mistake snowballs into a deliverability issue.
Cause #3: Your Unsubscribe Link Is Hard to Find
Nobody wants to see their email contacts to unsubscribe from their list. But the truth is not making the unsubscribe link obvious puts you in trouble with email deliverability problems.
You might assume—if someone doesn’t want my emails, they’ll unsubscribe it anyway, right? No, many won’t go hunting for the unsubscribe link buried deep into the email footer. If you don’t spare them the extra steps, they’ll take the shortcut: click Spam. This increases your spam complaint rate.
And now, it’s not just about being considerate or giving a good UX, it’s a sender requirement.
Both Gmail and Yahoo now demand that senders include a clear one-click unsubscribe option, and they expect unsubscribes to be processed within two days. If you don’t follow through, your emails may start getting blocked or filtered out of inboxes entirely.
Cause #4: You’re Still Emailing Unengaged or Inactive Subscribers
Sending to cold or disengaged contacts is a mistake that seems harmless on the surface. After all, you worked hard to build your list, right? But that logic doesn’t hold up with inbox providers.
When you keep sending to unengaged or inactive addresses:
- You get more bounces.
- You get more spam complaints.
- Inbox providers see low engagement and flag you as a spammy sender.
When inbox providers see consistent disinterest from the contacts, they assume you’re not a trustworthy sender. So, they start protecting their users from your emails.
That’s why high-quality email list matter way more than marketers think.
According to industry data, nearly 47.5% of marketers who regularly clean their emails lists say it helps protect their sender reputation with inbox providers. And over 25% say one of their biggest deliverability challenges is reducing bounces—which often come from emailing inactive or invalid addresses.
Cause #5: Treating Your Whole List the Same
Sending the same email to your entire list is convenient, but it leads to spam complaints. Users opted in, but they weren’t receiving emails that were useful to them. This happens because some marketers fail to segment their lists based on interests, behavior, purchase history, and other relevant factors. However, your audience consists of diverse individuals at various stages of life with diverse interests.
Say a person joins your newsletter but then starts getting product promos they don’t need. Eventually, they hit spam. Even if you’re not doing anything spammy, inbox providers notice low engagement. That hurts deliverability.
Even if your emails are technically allowed, sending irrelevant content repeatedly tells inbox providers that your emails aren’t valuable. That hurts your reputation.
Wrapping Up
Spam complaints don’t always stem from bad intentions or shady practices. Sometimes, even good marketers doing “all the right things” struggle with rising complaint rates and limping deliverability.
The fix isn’t a rapid-relief solution. But it’s not rocket science, either.
Here are a few practical things you can do to avoid those five common deliverability traps:
- Use a recognizable sender name.
- Stick to a sending frequency that your audience can handle.
- Make your unsubscribe link easy to find and easier to use. Follow the one-click unsubscribe practice.
- Follow the email list hygiene routine.
- Segment your list.
