InboxCheck
Clean and verify email lists without paying per-email
Quick background: I run a lead-gen/cold-email operation, so keeping email lists clean is something I deal with constantly. Every list I pull together ends up with a mix of typos, dead domains, disposable addresses, and generic role accounts (info@, support@) that just tank deliverability if you don't catch them.
The problem was the tools that do this — ZeroBounce, NeverBounce, etc. — charge per email. Every time I wanted to check a list, I was doing math on whether it was even worth it. For someone running lists regularly, that adds up fast, and it started to feel like paying a subscription just to use a spreadsheet.
So I built InboxCheck — a tool that runs entirely on your own machine, no per-email fees, no monthly subscription. You pay once and check as many lists as you want, forever.
What it actually does:
Validates email syntax and confirms domains have real mail servers (MX records)
Flags disposable/throwaway email domains
Flags role accounts (info@, support@, etc.) that hurt reply rates
Catches duplicates
Runs checks concurrently, so even large lists process in a couple of minutes instead of sitting there one row at a time
Spits out a color-coded Excel file (red = invalid, amber = free provider, lavender = role account, green = good to send) plus a summary tab
There's a GUI for anyone who doesn't want to touch a terminal, and a CLI for anyone who wants to script it into a bigger workflow.
It's a one-time $37 purchase — no recurring fees, because the whole point was to stop bleeding money every time I needed to check a list.
Still refining it, so if anyone here runs cold email or lead-gen lists and wants to kick the tires, I'd genuinely love feedback on what else would make it more useful.
[Link to Gumroad listing] · [Link to Indie Hackers product page]
#launched #show-ih
3 Comments
“‘No pay-per-email’ is a great differentiator.
Have you tested how much users actually trust the verification accuracy? In tools like this, perceived reliability usually matters more than pricing.”
What stood out to me was building both a GUI and a CLI. It feels like you’re acknowledging that this sits in different workflows depending on who’s using it.
Have you noticed whether most customers are running it as a one-off cleanup before a campaign, or does it become part of their regular lead-gen process?
The interesting tradeoff is replacing recurring verification costs with a one-time local tool.
What would convince you that the target users value avoiding per-email fees enough to switch, rather than preferring the convenience and integrations of existing verification platforms?