Why Your Emails Are Going to Spam (And How to Fix It)

Need the TLDR version? Jump to the bottom here!

You crafted the subject line. You wrote the copy. You hit send. And then nothing. Low opens, no clicks, zero replies. If that sounds familiar, there’s a good chance your emails aren’t reaching inboxes at all.

Here’s what most people don’t realize: when deliverability breaks down, the cause is almost never the platform you’re sending from. It’s your sending domain’s reputation, and it’s something only you can fix.

When an email lands in spam, it’s not random. Inbox providers like Gmail, Outlook, and Apple Mail use filters that evaluate your emails in real time, and they’re getting smarter every year.

These filters consider two things: technical signals (does this email come from a trustworthy source?) and engagement signals (do people actually want to read this?). If either is off, your emails get flagged before your subscriber ever sees them.

The fix depends on which category is causing the problem, so let’s walk through both.

Deliverability is a shared responsibility, and it’s worth understanding who controls what. 

Inbox providers consider two types of reputation: IP reputation (tied to the sending platform’s infrastructure) and domain reputation (tied to your sending domain). Both matter, but they are not weighted equally. Domain reputation carries significantly more influence over where your emails land.

Your sending domain (the part after the @ in your email address) builds its own reputation over time based on how recipients interact with your emails. Spam complaints, low open rates, bounces, and sending to people who never asked to hear from you. All of that is tied to your domain, not the platform you send from.

On the IP side, Flodesk actively manages our shared sending pools to keep them healthy. We monitor sending behavior across the platform and take steps to ensure that members with poor sending habits aren’t damaging pools used by members who are doing everything right .Of all the emails sent across our platform, only 0.1% bounce due to IP reputation—a direct result of how actively we manage our sending pools. Your domain reputation is where the real work happens.

When deliverability breaks down, the cause is almost always the same: domain reputation that’s been damaged by sending behavior. Switching platforms won’t fix it. Cleaning up your sending habits will.

The good news is that domain reputation isn’t permanent. It responds to consistent, quality sending, and the steps below are exactly what moves the needle.

For the first seven years, Flodesk didn’t charge by subscriber count, and for most members, that was a genuine advantage. But it can quietly create an environment for bad habits, which can lead to a deliverability problem if you’re not paying attention.

When there’s no cost tied to list size, there’s little urgency to clean it. Thousands of unengaged subscribers sit on a list indefinitely. Emails keep going out to people who stopped opening months ago. Inbox providers notice, and your domain reputation takes the hit for every email that gets ignored, deleted, or marked as spam.

Platforms that charge by subscriber count tend to see better list hygiene simply because there’s a financial reason to remove people who aren’t engaging. When it’s unlimited, that incentive disappears. Lists quietly accumulate dead weight and poor sending habits.

Think of your list less like an asset to accumulate and more like a garden to tend. The subscribers who are actively engaging are the ones doing the work to build your reputation. The ones who aren’t? They’re quietly working against it.

A smaller, engaged list will always outperform a large, disinterested one, in deliverability and in results.

Sending from a Gmail, Yahoo, or Hotmail address is one of the fastest ways to hurt your deliverability. In 2024, Google and Yahoo formalized requirements that bulk senders must use a custom domain—and it’s one of the first things spam filters check. Free email addresses are the calling card of spammers, which means legitimate business emails sent from them get caught in the same net.

The fix: use a custom domain email (like hello@yourbrand.com) for all your email marketing and make sure the domain is properly authenticated. This also makes your brand look more polished and builds trust with your subscribers from the very first email they receive.

Email authentication tells inbox providers that you are who you say you are. Without it, your emails look suspicious, even if your content is perfectly legitimate.

There are three records to know:

In Flodesk, you can set up your DKIM, SPF and DMARC records by going to Account Settings > Domain setup. The setup guide walks you through adding records to your DNS in under 10 minutes, or if you prefer, you can add them manually. 

One important note: authentication can drift. Something can change in the backend of your domain provider and quietly undo a setup that was previously working. Even if you’ve done this before, it’s worth checking again to make sure everything is still green.

This one surprises a lot of people. Shortened links from YouTube (youtu.be), LinkedIn, Bitly, TinyURL—any URL that redirects to another destination—are being flagged by inbox providers. We’ve analyzed sends across our platform and found that emails with shortened links see a 22% drop in open rates. Some of those emails aren’t just landing in spam. They’re triggering a warning banner that tells recipients there’s a dangerous link inside.

The fix is simple: use the full URL. If you’re sharing a YouTube video, open the video in your browser and copy the link directly from the address bar instead of using the share link. That small change alone has stopped emails from going to spam.

If you haven’t emailed your list all year and then send a big promotional blast to everyone on it, you’ve just bought yourself a one-way ticket to the spam folder. A sudden spike in volume looks like suspicious behavior to inbox providers. It can even resemble an account takeover. We see this clearly in our Flodesk data too. A sudden spike in volume can lead to a 43% increase in spam related bounces. 

The same applies when switching platforms or authenticating a new domain. You’re seen as a new sender and have to rebuild trust from scratch, regardless of your history elsewhere.

Warm up gradually. Start with your most engaged subscribers, increase your volume over a few weeks, and let your sender reputation build naturally before going wide.

This is the big one. When we look at members who write in with deliverability issues, consistent sending to unengaged subscribers is the root cause almost every single time, second only to unauthenticated domains. If someone isn’t opening your emails, sending to them doesn’t just waste your effort. It actively damages your domain reputation.

Inbox providers track engagement signals at the domain level. When they see your emails being ignored, deleted without opening, or marked as spam, they start filtering your future emails before they even reach the inbox, for everyone on your list, not just the unengaged subscribers.

The fix? Clean or segment your list often. Filter for subscribers who haven’t opened or clicked in the last 90 days, exclude them from your sends, and focus your energy on the audience that’s actually showing up for you. In Flodesk, go to Audience > Filter, set status to active, then add a filter for last activity that is not in the last 90 days. Add those subscribers to a “Cold” segment and exclude that segment from your sends going forward.

Here’s a counterintuitive truth: a subscriber who opened every email you sent for three years but went cold six months ago is less valuable to your sender reputation than someone who subscribed last month and has opened twice. Inbox providers weigh recent engagement far more heavily than historical behavior.

This changes how you should think about your list. Don’t protect long-tenured subscribers just because they were once loyal. What matters is who’s engaging now, and that’s exactly where your sending energy should go first.

Purchased lists, scraped contacts, or anyone who didn’t explicitly opt in to receive emails from you—these are your deliverability’s worst enemy. Not only are spam complaints more likely, but a disengaged list from the start tanks your domain reputation fast.

Build your list with people who actually want to be there. Use a clear opt-in, set expectations about what you’ll send, and deliver on those expectations consistently. If you’re in an industry where shared lists are common (events, trade shows, expos), resist the impulse to import them. The people who genuinely want to hear from you are worth waiting for.

Spam traps are email addresses used by inbox providers to catch senders with poor list hygiene. They are often pristine email addresses that have never opted into any marketing and can live on purchased lists. Hitting even one of them is enough to damage your domain reputation significantly.

Regular list cleaning is the best defense. Filter for subscribers who haven’t engaged in the last 90–180 days and remove or archive them before they do further damage.

Inbox providers don’t love surprises. Consistent, predictable sending builds trust. Going quiet for months and then blasting a big campaign looks suspicious, even if every person on your list opted in legitimately.

Domains tend to go cold after about four to six weeks of inactivity. If you’re not emailing at least monthly, you’re starting to lose the ground you’ve built. Consistency is one of the simplest things you can do for your deliverability, and one of the most overlooked.

Not sure if spam is actually the issue? Start by checking your domain reputation directly. It’s the fastest way to understand what inbox providers are seeing when your emails arrive.

Google Postmaster Tools (free) is the most useful starting point. It shows your domain reputation score with Gmail, your spam complaint rate, and whether your authentication is passing. Set it up at postmaster.google.com using the domain you send from. Note that it takes three to four days to update, so don’t panic if you don’t see data right away. Anything showing a “Bad” or “Low” reputation is your answer.

Keep a close eye on your spam complaint rate specifically. Google starts throttling your emails once that rate consistently exceeds 0.3%, a threshold that’s lower than most people expect.

From there, three more quick checks:

Deliverability issues feel frustrating because the problem is invisible. You can’t see what inbox providers are seeing until something is already wrong. But domain reputation responds to good sending habits faster than most people expect.

Here’s a quick summary of everything covered in this post:

Your sending infrastructure is solid. The rest is in your hands, and now you know exactly where to start.