BounceCheck

Clean a cold list before you send — dead addresses, throwaway domains and duplicates out first.

Check a list

Paste addresses (one per line, or a whole CSV — we'll pull the emails out), or upload a file. Your list stays on this device: the only thing that leaves is a DNS lookup of each domain, unless you add your own provider key below.

Mailbox-level checks (optional — your own provider key)

Format, duplicates, throwaway domains and dead domains are checked right here, free. Confirming that an individual mailbox exists — and whether a domain is catch-all — needs a verification provider. If you have a ZeroBounce account, paste your key and BounceCheck will run those checks through it, per address, on your quota. The key is stored only on this device, and addresses are sent only to that provider, only when you run a check.

How it works

1

Paste or upload

Drop in the list you were about to send — a spreadsheet export, an old sphere list, a stack of leads.

2

We check every address

Format, duplicates, throwaway domains, role inboxes, and whether the domain can actually receive mail (a live DNS/MX lookup per domain).

3

Send the clean list

Download the cleaned CSV, import it into MailBook, and send knowing the bounces were pulled before they hurt your deliverability.

What it checks — honestly

Checked here, for real

  • Format — broken addresses never reach a server.
  • Duplicates — the same address twice is a bounce-and-spam-complaint risk; extras are pulled.
  • Throwaway domains — checked against a built-in list of known disposable domains.
  • Dead domains — a live DNS lookup confirms the domain exists and has mail servers (MX). No mail server, no delivery.
  • Role inboxes — info@, support@, sales@ and friends get flagged, not silently sent.

Needs a provider key

  • Mailbox existence — whether this exact inbox is live can't be proven from DNS alone. Anyone who tells you otherwise from a web page is guessing.
  • Catch-all domains — some domains accept mail for every address, real or not. Detecting them takes a mailbox-level probe.
  • Add your own ZeroBounce key above and those rows stop saying “needs provider” and get a real verdict.

Made to sit with MailBook

BounceCheck is the front door for your sending. Clean the list here, then send from MailBook — the paired app lives in the same shelf and there's a BounceCheck entry right inside it, so the flow is: check → clean → send.

Open MailBook BounceCheck is free inside AgentOS

Built for realtors working cold and aging lists — expireds, old sphere, bought leads — where a 10–20% bounce rate is normal and every bounce makes the next send land in spam a little more.