You hit send, wait for replies, and nothing happens. This is a major issue when it comes to email marketing. Somewhere between your outbox and your customer’s inbox, your message took a wrong turn. When email drives your marketing or sales, that detour costs real money.
The upside? Deliverability issues aren’t random. They follow patterns you can measure and fix. Run a deliverability check, identify the main issues, then address them — that sequence is how you regain control of inbox placement.
How Providers Decide Where Your Email Goes?
Filters weigh hundreds of signals, not just a few “bad words.” They check whether you’re authenticated, how people react to your mail, and whether your domain or IP has a history. If too many red flags show up, your messages are pushed aside.
Deliverability platforms can run pre-checks on your campaign to predict how different providers will handle it. Instead of guessing, you see whether your email would get flagged, and you get guidance on adjusting the wording, links, or formatting before sending.
Fix the Foundation: SPF, DKIM, DMARC, and BIMI
Authentication is one of the biggest reasons behind the dreaded “email sent but not received by recipient” problem. If authentication is missing or broken, mailbox providers treat you like a stranger. Set up SPF to specify the servers that may send emails on behalf of your domain. Sign mail with DKIM so messages can’t be altered in transit. Add DMARC to tell providers how to handle anything that fails those checks.
BIMI is extra polish. It shows your brand logo, but only if you already enforce DMARC with 'quarantine' or 'reject'. Getting these records right is non-negotiable in today’s inbox landscape. A misconfigured record can stop a message before it even reaches spam. Most deliverability platforms test these records and guide corrections.
Reputation: The Email Version of a Credit Score
Your domain’s reputation rises when people open, click, reply, or move your mail into the inbox. It falls when they ignore you, bounce, or mark spam. Keep that score healthy by mailing people who opted in, honoring unsubscribes, and matching what you promised at signup.
Blocklists matter, too. If your IP or domain appears on a known list, some providers filter or drop your mail. Running a regular email blacklist check helps you spot these issues early. While deliverability tools can’t instantly remove you, they show which list you’re on and provide instructions to resolve the issue. But delisting only sticks when you fix the cause, such as an old scraped list or a risky signup form.
Content Can Still Hurt You
While filters don’t rely on a strict list of “forbidden words,” sloppy content can tip the balance. Overusing capital letters, packing your subject line with symbols, or linking through public URL shorteners raises suspicion. Providers care about context: one exclamation mark won’t hurt you, but combining aggressive formatting with poor reputation might.
Deliverability tools with content scoring highlight risky patterns so you can rewrite before sending. For example, “Grab yours now” reads human. “BUY NOW!!! LIMITED!!!” reads like a spam template.
List Hygiene and Engagement Signals
Emailing inactive or invalid addresses negatively impacts your performance. High bounce rates and consistently low opens tell providers your messages aren’t wanted, and delivery suffers as a result.
Think of your list like a guest list for a party. If half the guests don’t exist and the rest never respond, eventually you’d stop hosting. Providers do the same with neglected lists. Deliverability platforms help clean invalid contacts and identify who hasn’t engaged in months, letting you focus on the people who actually want to hear from you.
Engagement goes beyond list health. Providers pay attention when recipients reply, move your email to their primary inbox, or mark “not spam.” These actions carry more weight than open rates alone. That’s why platforms like Inboxally, an award-winning deliverability tool, focus on strengthening those engagement signals so providers see your emails as wanted.
Sending Habits That Backfire
Even with clean lists and solid content, sending patterns can trigger blocks. If you suddenly push out thousands of emails from a fresh domain, it looks like suspicious activity. Providers treat it as a stranger knocking on every door in the neighborhood at once.
Instead, deliverability tools help you gradually “warm up” your sending. The safest practice is slowly increasing your daily volume with real, opted-in recipients. Resist “warm-up” schemes that manufacture open or replies. Providers can detect synthetic engagement and may punish it.
Complaints Add Up Fast
Every spam complaint counts, and they add up quickly. Gmail’s new standards set a hard line: if your complaint rate consistently goes over 0.3%, delivery suffers. A good rule of thumb is to keep complaints under 0.1% — that’s about one complaint per 1,000 sends. Only mail people who opted in, make the unsubscribe button obvious, and send what they actually signed up for.
One or two complaints here and there aren’t catastrophic. Repeated spikes are the problem. Use deliverability tools to watch complaint trends; they’ll flag sudden jumps so you can fix the issue before ISPs start to push your mail out of the inbox.
Testing and Monitoring Placement
One of the most powerful things you can do is test before sending. Deliverability platforms let you preview how a message will land across different providers. They often use seed lists—test inboxes that give you a directional sense of placement. While these aren’t a perfect reflection of real recipients, they’re invaluable for spotting issues early.
Alongside testing, ongoing monitoring is key. Google’s Postmaster Tools show your domain’s reputation and spam complaint rate directly from Gmail. Microsoft’s SNDS provides similar insights for Outlook and Hotmail. Pairing these with your deliverability platform ensures you catch problems before they damage your campaigns.
Conclusion
Spam isn’t a mystery box. It’s the outcome of signals you can shape. Whatever the trigger, it can be fixed with the right mix of best practices and deliverability tools. Do that, and you’ll notice the change. Campaigns that land, get read, and move the needle. That’s deliverability working for you, not against you, and it’s a system you can keep healthy long after today’s send.