When your email campaign underperforms, deliverability should be one of the first things you check. If your message doesn't land in the inbox, it doesn't matter how brilliant your copy is or how enticing your offer sounds. Worse still, if your emails are being filtered into spam folders, it can damage your sender reputation further – a downward spiral that's tough to reverse.

One likely reason? You might be on a blacklist.

Major mailbox providers rely on these blacklists to help protect their users. If your domain or IP address is listed, your emails could be blocked entirely or filtered to spam. That means fewer opens, fewer clicks, and less return on your email marketing efforts.

So, how do you know if you're blacklisted?

That's where reputation management tools come in. They'll show whether you're on any major blacklists and offer guidance on how to clean up your sender reputation. If you find yourself on one, reach out to the list administrator – they'll typically advise you on what steps to take to improve.

But be warned: getting removed from a blacklist isn't a one-click fix.

There's a reason you were flagged. It could be your sending practices, poor list hygiene, lack of engagement, or all of the above. The key is to identify the most probable issue and fix it at the source.

And that brings us to one of the biggest culprits: a "dirty" email list.

If you're not regularly cleaning your list, you're putting your whole campaign at risk. Old, disengaged, or invalid email addresses can lead to bounces, spam complaints, and deliverability issues. Still, many marketers hang onto inactive subscribers in the hope they'll re-engage – despite the damage it could be causing.

Unfortunately, those same contacts may be sending your emails straight to the spam folder, which tells mailbox providers your content isn't wanted. That hurts your sender reputation even more.

In an upcoming article, we'll cover re-engagement strategies for lapsed subscribers. Spoiler: they'll only work on contacts who've recently gone quiet. If it's been six months or more since someone last opened an email, it's probably time to let them go.

After all, list quality beats list size – every time!