InboxCheck

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]