How it works
What probing is
Some mail servers say yes to every address, so for those a real one-line email checks the mailbox: delivered means it's real, and a bounce keeps it out.
Before an address can join a campaign, it's checked. Most mail servers will say whether a mailbox exists, but some say yes to everything. For those, a real email does the asking. That's a probe.
Every address is checked first
| The check | What it asks |
|---|---|
| Its domain | Does it take email at all? |
| Its mail server | Does it know this mailbox? |
| A probe | Only when the server can't say |
The answer is kept. The address isn't checked from scratch next time, on this list or any other.
Some servers say yes to everything
A catch-all mail server answers yes to every address. A real person: yes. A typo: yes. Someone who never existed: yes. So asking it proves nothing.
Those addresses aren't blacklisted. They're probed, and mailed only once the probe confirms them.
A real email gets the real answer
The probe is a real, one-line email called a mailbox check.
- If it's delivered, the address is real.
- If it bounces, the address never reaches your campaign.
A list's Clean tab counts the addresses still waiting on a probe: Why every list is cleaned shows where.
Probes stay apart from your sending
- Probes go out from their own mail server.
- They use their own domains, taking turns across them.
- They keep a steady pace for each mailbox provider.
They run apart from your campaigns.
Why it's worth it
Every bounce tells the mailbox providers a list is out of date, and they remember. Probing keeps those addresses out, so you get fewer bounces, a cleaner sending record, and more of your mail in the inbox.
Related
- Why every list is cleanedBefore anything sends, every address is checked, so only real, working addresses are mailed and typos, dead mailboxes, unsubscribes and spam reports are kept out.How it works
- Upload and clean your listMake a list, upload your contacts as a CSV, check the columns and confirm consent. Every address is cleaned on the way in, then checked with its own mail server.Step by step · 13 steps
- How a sign-up form fills your listA sign-up form on your website adds people to one list, keeps bots and throwaway addresses out, and has every new address checked before it's ever mailed.How it works
- A campaign that protects itselfOnce 1,000 emails have gone out since it last started, a campaign pauses itself if 3 in every 100 bounce hard, and a variant that draws spam reports is paused on its own.How it works