How to Detect Suspicious and Spam Email Addresses in Google Sheets

A subscriber list full of fake, disposable, or bot-generated emails doesn't just inflate your numbers — it can hurt your domain reputation, increase unsubscribes, and cause deliverability issues in Mailchimp. The problem is that manually reviewing hundreds or thousands of rows isn't practical.

Sheets2Mailchimp includes a spam detection tool (Starter plan and above) that scans email addresses on your active sheet, flags ones that look suspicious, and helps you review them before syncing to Mailchimp. This guide explains what it does, how to use it, and what to do with the results.

Plan note: spam detection is not included on the free plan. You need Starter or a higher plan to run scans and see results. The Free plan still includes manual sync and other basic features.

Why review potentially spam emails?

Low-quality subscribers often end up on your list through:

• Open signup forms hit by list bombing (hundreds of fake signups at once).
• Disposable addresses (Mailinator, Guerrilla Mail, 10MinuteMail, etc.) that never open your campaigns.
• Generic or system addresses (noreply@, admin@, test@) that aren't real contacts.
• Cheap or suspicious domains commonly used for automated signups.

Mailchimp penalizes lists with high bounce and unsubscribe rates. Cleaning your sheet before importing or syncing is one of the cheapest ways to protect your audience.

What does spam detection do?

The Detect Spam feature scans the email column on your currently active sheet and applies several heuristic checks. It does not delete any contacts — it only flags suspicious rows so you can decide what to do.

Checks include:

The tool compares each address against a large list of known disposable domains and applies the rules above automatically.

Sheet requirements

For the scan to work correctly:

1. Row 1 must be the header with column names.
2. You need a column named Email, Email Address, or Email_address (case-insensitive).
3. Subscriber data starts on row 2 onward.
4. The scan always runs on the active sheet (the tab you have selected).

If the email column isn't found, you'll see an error message. Rename your column or duplicate the sheet with the expected format.

How to use spam detection step by step

Step 1: Open the add-on (Starter plan or above)

1. Open your Google Sheet with subscriber data.
2. Go to Extensions > Sheets2Mailchimp to open the sidebar.
3. On the add-on home screen, click Detect Spam.

If you're on the Free plan, the add-on will prompt you to upgrade to Starter to use this feature. With an active paid plan, you'll see a card summarizing the checks and which sheet will be scanned, along with the approximate number of data rows.

Step 2: Run the scan

Click Scan Now. The add-on goes through every row with an email and counts how many addresses look suspicious.

Step 3: Review the results

After the scan you get the full report:

• Suspicious rows are highlighted in yellow (#FFF2CC) across the entire row in your sheet.
• The sidebar lists flagged emails (up to 20 on screen; if there are more, a note shows the rest).
• For each one you see the row number and reason (e.g. "Disposable email domain", "Role-based address", "Suspicious TLD (.tk)").

Important: the yellow highlight is visual only. No emails are deleted automatically. You decide whether to delete the row, fix the address, or exclude that contact from the next sync.

Step 4: Clean up and scan again if needed

After reviewing:

• Remove or fix rows you confirm as junk.
• Optionally click Scan Again to verify no suspicious addresses remain.
• When you're satisfied, continue with your usual sync to Mailchimp.

Best practices: when to run a scan

We recommend using spam detection at these times:

• Before your first sync with a new sheet or data imported from another system.
• After a spike in signups on a public form (possible list bombing).
• Periodically if several people add rows to the same sheet manually.
• After merging lists from different sources (events, old spreadsheets, third-party CSVs).

A simple workflow:

Import or update data → Detect Spam → Review yellow rows → Sync to Mailchimp

That way you avoid uploading contacts you already knew were questionable.

What to do with a flagged email (and when not to delete)

Not everything the tool flags is malicious spam. Some cases deserve a manual look:

• info@ or contact@ for a small business — May be legitimate if it's their only address, even if it's not ideal for newsletters.
• .tk or other cheap TLDs — Some real projects use them; consider context (name, history, signup source).
• Odd but real addresses — If you know the subscriber, don't remove them based on heuristics alone.

Detection is a way to prioritize review, not a perfect filter. When in doubt, look for extra signals: empty name fields, bulk signup dates, or form source.

Plan availability

According to the Sheets2Mailchimp pricing table:

Spam detection is included starting with the Starter plan (from $6/month), along with Campaign Reports and higher sync limits. Pro and Enterprise also include it, with more daily syncs and more subscribers per sync.

Frequently asked questions

Does the tool verify that the email exists or can receive mail?
No. It does not perform SMTP verification or server "ping" checks. It only analyzes patterns associated with low-quality addresses.

Can I scan multiple sheets at once?
Not in a single pass. Switch to the tab you want to analyze, make it active, and run the scan again.

Does the yellow highlight go away on its own?
No, not automatically. You can clear background color in Google Sheets (Format > Clear formatting) or delete rows you no longer need.

Does the scan affect my Mailchimp account?
No. Everything happens in your Google Sheet until you choose to sync.

Should I delete every flagged email?
Not necessarily. Use them as a priority review list. Only remove or exclude addresses you confirm as invalid or unwanted.

Can I use Detect Spam on the free plan?
No. The Free plan includes manual sync (up to 3 syncs/day and 50 subscribers per sync), but not spam detection. You need Starter or above to access this tool.

Conclusion

Keeping a clean audience doesn't require external tools or exporting CSVs to validation services. With Detect Spam in Sheets2Mailchimp, you can review potentially spam emails right in the sheet where you already work, highlight questionable cases, and sync to Mailchimp with more confidence.

Ready to try it? Install Sheets2Mailchimp from the Google Workspace Marketplace and, with a Starter plan or above, open your subscriber sheet and click Detect Spam in the sidebar. See plans and pricing if you want to upgrade from Free to Starter.