Episode 05 / 5
Email Verification and List Cleaning
Why bounces hurt your sender reputation, how email verifiers work, and a six step flow to clean a list before you send.
What you'll learn
- Hard versus soft bounces, and why bounces damage sender reputation.
- How a verifier works, and what valid, invalid, unknown and disposable mean.
- Role based addresses, spam traps, and three ways to handle catch all domains.
- Why a verified email isn't the right lead: duplicates, wrong people, ICP mismatch.
- Keeping names right: accents, capitals and prefixes like van der or O'Brien.
- The suppression list and a six step cleaning flow: send, test, don't send.
Chapters
Full text
The send button, and the bounces
Your list is ready. Two thousand people. All of them fit your ICP. You hit send. An hour later, a hundred and eighty emails bounce. None of these people saw your message. But Gmail and Outlook saw you trying to write to addresses that don't exist. And your emails to the right addresses may pay the price too. The problem wasn't the message. It was the list. In this episode, we set up how to verify and clean a list before you send.
Bounces and sender reputation
First, the word: bounce. An email that comes back without being delivered. A hard bounce is a permanent rejection. The address or the domain doesn't exist. For example, the closed account of someone who left the company. A soft bounce is a temporary rejection. The mailbox is full, or the server is busy at that moment. The error codes make the difference clear: codes starting with five are permanent, codes starting with four are temporary. An address that hard bounces never goes back on the list. A soft bounce gets retried; if it keeps coming back, it goes too. In episode three, we talked about sender reputation. Gmail and Outlook watch your domain's behaviour all the time. A sender who writes to addresses that don't exist looks careless. Yahoo asks you to track your bounces. Microsoft asks high volume senders to clean out invalid addresses regularly. And Google sets a clear limit for spam complaints: below three in a thousand, and ideally below one in a thousand. There's no official threshold published for bounces. The common practice is to keep hard bounces below two percent, ideally below one percent. Not a law, a safety margin. The goal: remove every address you know will bounce, before you send.
How a verifier works, and what its labels mean
For that, we use a verifier: a verification tool. Without sending an email, it checks in three layers whether the address will accept a message. The first is syntax. Is the at sign missing? Has a space crept in? The second is the domain. Does the domain have a server to receive email, an MX record? If not, the email can't go anywhere. The third is the SMTP check. The verifier tells the server: I have a message for this address. If the server says there's no such person, the address is invalid. The conversation ends before any message is sent. Nothing lands in the inbox. So why isn't it a hundred percent? Because not every server gives a clear answer. Some say yes to every address. Some make unknown senders wait. Some sit behind security layers that never answer at all. So a verifier's result isn't a certainty. It's a risk estimate. Every address gets a label. The names change from tool to tool, but the logic is the same. Valid. The mailbox exists and accepts email. Safe to send. Invalid. The mailbox doesn't exist, or the domain doesn't take email. A certain hard bounce. Remove it. Unknown. The server didn't give a clear answer. Not a rejection, just uncertainty. Verify again a few hours later. If it's still unclear, keep it out of the main send. Disposable. Throwaway addresses. They have no place on a B2B list. Remove them.
Role based addresses, spam traps and catch all
Role based addresses. Like info, sales or support: addresses that belong to a function, not a person. They're often valid. But the message doesn't reach anyone personally, and the complaint risk is higher. If the person has their own address, don't use the role based one. A spam trap is a trap address. Some never belonged to anyone; some are old addresses that were closed and turned into traps. Sending to a trap tells the providers you built your list carelessly. And let's be honest: no verifier can see every trap. Tools only flag the known ones. The best protection is not to build your list from old addresses, unknown sources, or addresses scraped from the web. Now the most confusing label: catch all. Catch all, or accept all, is a setting for the whole domain. Whatever address you write to, the server says yes at first. To a real employee's address, and to a name you made up. A classic verifier can't tell the two apart here. It writes catch all and leaves the decision to you. There are three ways forward. One: keep them separate. Don't mix them into the main campaign. Two: use a verifier that specialises in catch all. These tools try to assess addresses one by one, again without sending. But there's no hundred percent here either. Three: a small test group. Say, fifty addresses. If the bounce rate is low, grow it; if it climbs, stop. The TechSales app cleans the list too: it verifies emails, uses Reoon and BounceBan for catch all addresses, and scores ICP fit.
The right lead, and names written right
Still, a verified email doesn't mean the right lead. One: duplicates. The same person may have come from two sources. Two emails on the same day ends the first impression. Two: the wrong person. They left the company, or they're outside the persona. The email is valid; the person is wrong. Three: ICP mismatch. In episode two we said twenty to two hundred employees. What is a five thousand person group doing on the list? Four: missing fields. If the first name or the company is empty, personalisation breaks. Then there's formatting. Names deserve their own section. Names often arrive all in capitals, all in lower case, or with their accents stripped. For example, a surname in capitals: MÜLLER. Fix it with a standard formula and you may get Muller, without the umlaut. Or José turns into Jose, and Łukasz into Lukasz. Prefixes break too: van der Berg, de la Fuente, O'Brien, McDonald. A simple capitalise rule gets most of them wrong. Make sure your tool keeps accents and handles prefixes, and check the first rows with your own eyes. Is it Muller or Müller? If you're not sure, go back to the source. Never guess a name. Titles arrive mixed too: one row says Director Comercial, another says Head of Sales. Bring them into one standard. Filtering gets easier, and the message reads properly.
The suppression list and a six step flow
Next is the suppression list. The list of people you will never write to. Current customers. Companies with an open sales conversation. Competitors. Everyone who said don't write to me. And accounts you've been told not to touch. Every new list is checked against it. For opt outs, the address is excluded; for customers and competitors, the whole domain. If someone told you by email not to write to them, you don't go to them on LinkedIn either. And then there's time. People change jobs, accounts get closed. If your list has been waiting for weeks, verify it again right before you send. Verification isn't a one time job. It's the last step before every send. Now let's put it all into one flow. Each row is a lead. One: remove duplicates. Two: the suppression check. Customers, competitors and opt outs drop out. Three: the ICP and persona check. Don't delete a row that doesn't fit; write the reason next to it. Four: clean up the first name, last name, company and title. Five: verify, and record the result and the date. Six: split. Valid goes to the main campaign. Catch all and unknowns that stay unclear go to a test group. Invalid, disposable and suspected traps go out. In the end, three groups: send, test, don't send. And every decision has a reason.
Responsibility, and the next episode
Finally, responsibility. Anyone who wants out, whichever channel they say it on, goes on the suppression list permanently. It's respect, and in many countries it's a legal requirement. The GDPR asks that data be linked to a purpose, limited and proportionate. Don't collect or keep information you don't need. The rules for marketing to business addresses differ from country to country. But the right to say no exists everywhere. This isn't legal advice. Talk to a lawyer about your own situation. To sum up: bounces are reputation, and a verifier is an estimation tool. And a clean list isn't just valid addresses. It's the right person, with their name written right. A small exercise you can try right away: take a hundred rows from your list. Remove duplicates and anyone on your suppression list, then verify the rest. Then mark every row as send, test or don't send, and write the reason next to it. How much the send group shrinks shows you the real state of your list. We now have a clean list. Next comes the part everyone asks about: what do we write to these people? In the next episode, we'll talk about how we write a cold email, from the subject line to the first sentence and a clear call to action. You'll find the other episodes at techsales tr dot com, slash academy. See you next time.
Build this system yourself.
TechSales brings ICP scoring, list verification, email and LinkedIn campaigns and every reply into one place.