What are common root causes of deliverability problems?

Your emails aren't landing in the inbox, and you want to know why. The frustrating truth is there are usually five places the problem hides, and they don't always announce themselves clearly. Here's how to think through each one.

Authentication failures are the first thing to rule out. If your SPF, DKIM, or DMARC records are broken or misaligned, mailbox providers have a hard time trusting your mail before they even look at your content. Check your email headers or run a quick DNS lookup. If your SPF record includes too many lookups, your DKIM selector is missing, or your DMARC policy is set to none without any monitoring in place, that's your starting point.

List quality problems are the second most common culprit. Old addresses, unengaged subscribers, and invalid contacts create bounce rates and spam traps that signal to mailbox providers that you're not managing your audience well. If you bought a list at any point, that history follows you. If your list hasn't been touched in a year or more, treat it as suspect until you've cleaned it.

Reputation damage often shows up after the other two have gone unaddressed for a while. High complaint rates, blocklist listings, and low engagement patterns compound over time. You can check whether your sending domain or IP has landed on a blocklist with our free blocklist checker. A single complaint spike from a bad campaign can leave marks that take weeks to recover from.

Sending practice issues are sneaky because they feel like normal business decisions. Jumping from 500 emails a week to 50,000 without warming up your volume, going silent for two months and then blasting your full list, or sending to everyone regardless of engagement all look like red flags to filtering systems. Consistency matters more than people expect.

Content problems are real but often overblamed. Spam trigger words, broken links, or a wildly off-balance image-to-text ratio can push you into the spam folder, but content alone rarely tanks deliverability if everything else is healthy. If authentication, list quality, reputation, and sending patterns are solid, content becomes the tiebreaker, not the main event.

Most deliverability problems trace back to one of these five areas, and most serious cases involve more than one at once. The fastest way to narrow it down is to check your data sources in order: authentication first, then bounce patterns, then complaint rates, then blocklist status. That sequence saves a lot of guessing.

But if you're stuck on where to start, our SOS hotline is free. No pitch, just help figuring out which of these is actually hurting you right now.