What is deliverability troubleshooting?

Your open rates just dropped. Or a customer says they never got your confirmation email. Or your ESP flags a deliverability warning and you're not sure where to start. That's the moment deliverability troubleshooting begins.

Deliverability troubleshooting is the process of figuring out why your emails aren't reaching the inbox and fixing whatever's causing it. It's part detective work, part systems check, part patience.

In practice, it breaks down into four moves. First, you spot that something's wrong (metrics, bounce logs, a user complaint). Second, you dig into the cause. Third, you fix it. Fourth, you verify the fix actually worked.

The tricky part is step two, because the cause could be very different things. Problems usually fall into one of three buckets:

• Technical issues cover broken or missing authentication (SPF, DKIM, DMARC), DNS misconfigurations, and sending infrastructure problems. These are often the easiest to confirm and fix.
• Reputation issues cover blocklist appearances, high spam complaint rates, and a damaged sender reputation. These take longer to recover from.
• List quality issues cover old or unengaged subscribers, invalid addresses, and spam traps hiding in your data. These sneak up on you slowly and get bad fast.

What separates good troubleshooting from guessing is data. You need bounce logs, authentication reports, engagement metrics, and access to postmaster tools (like Gmail Postmaster Tools or Outlook's SNDS) to see what the mailbox providers are actually seeing.

And knowing the difference between a temporary blip versus a systemic problem matters a lot. One bad campaign can cause a dip. A broken authentication record can quietly tank your reputation for weeks before you notice.

If you're staring at a sudden drop and not sure where to start, our SOS hotline is free and we don't bite ;)