I used to pay per-email every time I verified a list. Now I run unlimited checks on my own machine for a flat $37. Here’s the full breakdown.
If you run cold email or lead-gen campaigns, you know: your list is only as good as the emails in it. Send to enough dead addresses, disposable domains, or generic role accounts, and your deliverability tanks – sometimes permanently.
Grab a Complimentry Growth Plan for Your Business.
Hit the Blue Button and see what’s possible….
The usual fix? A verification service. Tools like ZeroBounce or NeverBounce will check your list – for a per-email fee. Run a few thousand-address list every week or two, and the bill stacks up fast.
So I built my own.
The Per-Email Problem
For anyone doing this regularly, the math gets ugly. You’re not checking a list once – you’re checking new lists constantly. Every check costs money, so you start rationing something that should be a basic hygiene step. That’s backwards.
There’s also a trust issue. You’re uploading your leads – a list you’ve spent real time or money building – to someone else’s server. For a lot of people, that’s one more thing they’d rather not think about.
What I Built Instead
InboxCheck runs entirely on your machine. No per-email charges. No subscription. Nothing leaves your computer. You pay once and check as many lists as you want, forever.
Here’s what it does under the hood:
–Syntax and domain validation – catches typos and malformed addresses before they hit your sending tool
–Real MX record checks – confirms the domain can actually receive mail
–Disposable domain detection – flags throwaway addresses people use to dodge your outreach
–Role account flagging – info@, support@, admin@ and similar addresses rarely convert and can hurt sender reputation
–Duplicate detection – messy lists usually have more overlap than people expect
–Concurrent processing – checks run in parallel, so large lists finish in minutes
The output is a color-coded Excel file: green for good to send, amber for free providers, lavender for role accounts, red for invalid. Plus a summary tab so you can see the health of your whole list at a glance.
Simple GUI if you’d rather not touch a terminal. CLI if you want to fold it into an automated workflow.
Who This Is For
If you verify lists often enough that per-email fees become a recurring cost worth avoiding, this is for you. Cold email operators, lead-gen agencies, freelancers running outreach for clients – anyone who treats list hygiene as a routine step.
If you send the occasional campaign, a free online checker is probably fine.
Try It
InboxCheck is a one-time $37 purchase on Gumroad. No recurring fees – because the whole point was to stop bleeding money every time a list needed checking.
If you’re already running cold email at any volume, I’d love to hear what you think – or what would make it more useful for how you work.