How to set up custom spam filter tests in Folderly for your GTM initiatives

If you’re running go-to-market (GTM) campaigns, you know how much your results depend on your emails actually landing in inboxes instead of spam folders. But here’s the thing: most tools run generic spam checks that don’t reflect your real audience or messages. That’s where custom spam filter testing comes in—and why it matters if you want your outreach to actually work.

This guide is for GTM teams, marketers, founders, or anyone responsible for sending bulk or cold emails and who’s tired of guessing why their outreach gets ignored. We’ll walk through how to set up custom spam filter tests in Folderly so you get honest feedback on your deliverability. No fluff, no magic tricks—just what works, what doesn’t, and how to avoid wasting your time.

Why Custom Spam Filter Tests? (And Why Most Advice is Useless)

Let’s get this out of the way: built-in “spam score” meters in most email tools are about as useful as a horoscope. They’re generic, don’t reflect your unique sender reputation, and almost never mimic the filters your real prospects use.

Custom spam filter tests let you:

  • See how your audience’s mail servers will react, not just a random test mailbox.
  • Test your actual templates, domains, and sending IPs, not some sanitized demo version.
  • Stop playing whack-a-mole with “spam words” and start fixing the real problems (like authentication, reputation, and technical missteps).

If you’re sending more than a handful of emails for GTM, you need this.

Step 1: Prep Your Folderly Account

First, you need access to Folderly. If you’re new, sign up and go through their onboarding. (This part isn’t rocket science, but don’t skip their initial setup—half of deliverability issues start with misconfigured DNS or sender domains.)

Checklist: - Your sending domain is verified and authenticated (SPF, DKIM, DMARC are set up). - You can send test emails from your actual GTM campaign mailbox. - You know which campaign, template, or sending identity you want to test.

Pro Tip:
Don’t run tests from a demo or “test” mailbox. Use the actual mailbox and domain you’ll be sending from. Spam filters look at sender history and reputation, so you want the real thing.

Step 2: Understand Folderly’s Testing Tools

Folderly offers a couple of testing options:

  • Basic Deliverability Test: Sends test emails to a network of seed mailboxes and checks where they land (Inbox, Spam, Promotions, etc.).
  • Custom Spam Filter Test: Lets you set up more targeted tests—using your own templates, sender identities, and even custom recipient lists.

If you’re serious about GTM, you want the custom test. The default tests are fine for a quick health check, but they’re too generic for campaign work.

Step 3: Set Up a Custom Spam Filter Test

Here’s how to set up a test that actually tells you something useful.

3.1. Pick the Right Sending Identity

  • Log in to Folderly.
  • Go to the “Deliverability Tests” or “Spam Tests” section.
  • Select the exact mailbox and sending domain you’ll use for your GTM campaign.

Don’t skip this. Results from a different mailbox/domain are meaningless.

3.2. Build Your Test Template

  • Use the real email copy you’ll send in your campaign—don’t water it down or change “spammy” words just for the test.
  • Include your signature, images, links, and any personalization tokens.
  • If you use dynamic content, test both a “worst case” (most links, most images) and an “average” version.

What to ignore:
People obsess over “spam words.” In reality, filters care more about sender reputation, authentication, and engagement history. Don’t waste hours re-writing copy just to please a spam checker.

3.3. Set Up the Recipient List

  • Folderly’s default seed list is fine for a baseline, but you can upload your own addresses if you want to mimic specific recipients (say, Gmail business users or Outlook users).
  • For GTM, try to include addresses on the same platforms your prospects use.

Pro Tip:
If you’re targeting mostly corporate inboxes (like Google Workspace or Office 365), focus your test on those. Consumer Gmail and Yahoo react differently than business mailboxes.

3.4. Run the Test

  • Hit “Start Test” or equivalent.
  • Folderly will send your test emails and start gathering results.

Depending on your plan, it may take a few minutes to an hour for full results.

Step 4: Read (and Actually Use) the Results

Here’s what Folderly will show you:

  • Where your email landed: Inbox, Promotions, Spam, or not delivered.
  • Which mail providers flagged your message: E.g., Gmail spammed it, but Outlook didn’t.
  • Authentication issues: Missing or failing SPF/DKIM/DMARC checks.
  • Technical problems: Broken images, sketchy links, blacklisted IPs/domains.

What Matters

  • Inbox rate with your target mailbox types (not just the overall average).
  • Consistent issues across providers: If Gmail and Outlook mark you as spam, it’s probably your authentication or domain reputation.
  • Authentication failures: Fix these first. No amount of copy-editing will save you if your SPF or DKIM is broken.

What Doesn’t Matter (Much)

  • The “spam score” number. These are rough guesses.
  • Minor variations between test runs. Filters fluctuate a bit.
  • Warnings about “spammy language.” Focus on technical fixes first.

Step 5: Fix Issues and Retest (This Is Normal)

Don’t expect a perfect score the first time. That’s normal.

Common fixes:

  • Authentication: Double-check SPF, DKIM, and DMARC. Use external tools like MXToolbox or Google Postmaster Tools if you’re unsure.
  • Domain or IP reputation: If your domain is new or your sending IP is shared with spammers, consider warming up or switching providers.
  • Technical content: Broken images or links, sketchy URL shorteners, or attachments can all hurt you.

What not to do:
Don’t obsess over one test. Run a few tests, tweak, and watch for trends. If you’re still hitting spam after several rounds, you might need to pause and rethink your sending practices or even your domain.

Step 6: Integrate Testing Into Your GTM Workflow

Custom spam filter testing shouldn’t be a one-and-done thing. Make it part of your pre-flight checklist for every new campaign.

  • Before launch: Run a test with your final template and sender.
  • After tweaks: If you make big changes (copy, design, sender), test again.
  • Ongoing: Spot-check every few weeks, especially if results drop.

Pro Tip:
Document your test results over time. If you suddenly get blocked, you’ll have a trail to help diagnose what changed.

Honest Takes: What Works, What’s Overhyped

  • Works:
  • Testing with real sender identities and templates.
  • Fixing authentication and technical issues before worrying about copy.

  • Focusing on your actual audience’s mail providers.

  • Overhyped:

  • Chasing “spam words” or obsessing over AI-generated copy tweaks.
  • Trusting a single test result as gospel.

  • Thinking Folderly (or any tool) can fix years of bad sender reputation overnight.

  • Ignore:

  • Generic spam checker scores that don’t match your audience.
  • Advice to “just warm up your domain for a few days”—real reputation takes time.

Keep It Simple (and Keep Testing)

Don’t let spam filter testing turn into a science project. Use Folderly’s custom tests to spot big issues, fix the basics, and get your GTM campaign out the door. Iterate as you go—campaigns that get stuck in endless “deliverability tweaking” mode rarely ship anything worth measuring.

Stay focused on your real audience, fix what actually matters, and don’t fall for overhyped shortcuts. The goal isn’t a perfect score—it’s a real response from someone who actually saw your email.

Good luck, and keep it simple.