If you send marketing emails or newsletters, you already know how quickly a few bad sends can tank your sender reputation. Maybe you keep hitting spam traps, or you get too many complaints. Either way, it’s a headache. Custom suppression lists help you stop those mistakes before they happen. This guide walks you through how to build and use custom suppression lists in Kickbox — without getting lost in the weeds.
This is for anyone managing email lists who wants to actually reach people, not their spam folders. Whether you’re a solo creator or wrangling lists for a company, you’ll find practical steps here (and fair warning about what not to bother with).
Why bother with custom suppression lists?
Let’s get real: most email platforms, including Kickbox, have basic suppression lists baked in (think: hard bounces, unsubscribes, and complaints). That’s table stakes. But those don’t catch everything that can damage your reputation, like:
- People who always mark you as spam but never unsubscribe
- Temporary blocks (e.g., someone’s mailbox is full for weeks)
- Internal competitors or test addresses you never want to email
- Role accounts (like
info@orsupport@) that never engage
Relying only on automatic suppression is like locking your front door but leaving the windows wide open. Custom suppression lists let you lock down the rest.
Pro tip: The more you avoid hitting bad addresses, the less likely you are to get blacklisted or throttled.
Step 1: Decide what you actually want to suppress
Before you start clicking around, get clear about who shouldn’t get your emails. Don’t just copy and paste every “problem” address you find — that creates more noise than value.
Here’s what’s actually useful to suppress:
- Chronic complainers: People who mark you as spam more than once. They’re not going to change.
- Known spam traps: If you have a list of addresses that triggered traps before, block them.
- Competitors, partners, or internal addresses: Accidental sends here can get awkward, fast.
- Unengaged addresses: Folks who haven’t opened or clicked in a year? Might as well suppress them before they hurt your stats.
- Problematic domains: Sometimes entire domains (like disposable email providers) are more trouble than they’re worth.
What to ignore:
Don’t overthink every soft bounce or one-off unsubscribe. There’s no need to suppress someone forever because their inbox was full for a day.
Step 2: Prepare your suppression data
Kickbox accepts suppression lists in basic CSV or TXT formats. You need just the email addresses (no names, no extra columns). Keep it simple.
A few tips:
- Save your file as
suppression-list.csvor.txt. - If you handle multiple types of suppressions (e.g., spam traps vs. internal), use separate files. Don’t mix everything together unless you really mean to.
- Double-check for typos. Suppressing
jane@gnail.comisn’t going to help anyone.
Example CSV:
email badaddress1@example.com spamtrap@shady-domain.com info@yourcompany.com
No need for fancy formatting. Kickbox isn’t picky here.
Step 3: Upload your custom suppression list in Kickbox
Now, the actual “how-to” part.
- Log in to your Kickbox account.
-
If you’re not already using Kickbox, you’ll need an account. And yes, the suppression features are available even on basic plans.
-
Navigate to the Suppression Lists section.
-
Usually under the “Deliverability Tools” or “Suppression Lists” tab. If you don’t see it, check your plan or ask support (they’re actually helpful).
-
Choose ‘Create New Suppression List’ or ‘Import’ (wording may vary).
-
Name your list something you’ll remember — not just “List 1.” Try “2024-internal-suppression” or “SpamTraps-Q2”.
-
Upload your CSV or TXT file.
-
Drag and drop, or browse to select your file.
-
Confirm and review the imported addresses.
-
Kickbox will usually show you what’s being added. Double-check for weird entries or accidental blanks.
-
Save and activate the list.
- Some platforms make you “activate” a new suppression list to start blocking sends. Don’t skip this.
Honest take:
Uploading is dead simple. The hard part is keeping your suppression lists up to date — not the software itself.
Step 4: Apply your suppression list to your sends
A suppression list only helps if you actually use it. Here’s what to watch for:
- Connect your suppression list to each campaign or integration.
- In Kickbox, you usually select which suppression lists to apply when setting up a send or syncing with an ESP (like Mailchimp, SendGrid, etc.).
-
If you forget this step, your custom suppressions won’t do a thing.
-
Automate where possible.
-
Some integrations let you auto-sync suppression lists. If you’re pulling in new spam traps or unsubscribes from other tools, set up automation to update your Kickbox list, too.
-
Test before blasting.
- Always run a small test send to see if the suppression is working. No shame in double-checking.
Pro tip:
Suppression lists aren’t retroactive. If you add new addresses tomorrow, they’ll only be suppressed from future sends.
Step 5: Maintain your suppression lists regularly
This is the part nobody wants to do, but it’s what keeps your sender reputation from sliding.
- Set a monthly calendar reminder to review and update your lists. Don’t wait until you have a deliverability crisis.
- Export new spam complaints or bounce lists from your ESP and add them to your custom suppressions.
- Remove addresses you accidentally suppressed (it happens), but only if you’re sure they’re safe.
What doesn’t work:
Don’t try to build a “perfect” suppression list. Email addresses change, new spam traps pop up, people move jobs. Focus on catching the worst offenders and iterate as you go.
What about dynamic suppression? (A reality check)
Some vendors hype “real-time suppression” or “AI-powered suppression lists.” Sounds fancy, but for most senders, it’s overkill or a budget drain.
- If you’re sending millions of emails daily, maybe explore automation.
- For everyone else, a good manual review every month or two is more than enough.
- Don’t pay extra for features you won’t actually use.
Skip the hype.
A basic, well-maintained custom suppression list does 90% of the job.
How to know if your suppression list is working
Don’t just trust the checkbox. Watch your metrics:
- Lower bounce rates: Should drop after suppressing bad addresses.
- Fewer spam complaints: If you’re still getting a lot, dig deeper.
- Better open/click rates: Not a magic bullet, but you’ll see improvements if you’re removing deadweight.
If nothing improves, your problem might be with content or list quality — not suppression. Don’t blame the tool.
Keep it simple: Focus on progress, not perfection
Custom suppression lists are like flossing: a little effort now saves you a ton of pain later. Don’t let the process get so complicated you stop doing it. Start with the obvious addresses, keep your lists tidy, and update regularly.
Iterate as you learn. If you notice new patterns — like a certain domain keeps bouncing — add it. If you made a mistake, fix it next month. No need to chase every trend or shiny new tool.
The goal isn’t to make your suppression list perfect. It’s to make your sending safer, cleaner, and less stressful. And that’s a win for your reputation.