Time to time, we have customers who get back to us saying, your software didn't clean all the bounced email addresses or I have a lot of bounces even after using your verification software. Here's an explanation for that...
You must take note that we don't guarantee 100% bounce removal.
We only guarantee 90-95% but with real-time bounce processing added in (where we literally send out verification emails to your customers), that figure can go up to 98%.
We can assure you that no one in our industry is even close to those figures. What we do request is a copy of those bounced emails. This way, our developers can train the system if there is anything more we could do to improve the verification process. So the next time you run the verification jobs with similar domains, we have an improved verification system that could try to catch these.
Now there are a number of reasons why our system would mark emails as valid but it ends up as bounced address.
1) The mailbox is full (this is the most common one). So although the mailbox is available and ready to receive messages, it just can't accept any further messages because it hasn't been used for a long time.
2) The catch-all addresses. This is when the mail server accepts any message delivered to its mail servers (Eg. *@domain.com). These addresses are particularly harder to verify because nearly 90% of the time, they are valid but that rest of 20% can sometimes cause bounces. You can go to our competitors and they do no better job at identifying these. We are still developing technology that could eliminate this. So far, we've come up with real-time bounce processing which eliminates nearly 98% of bounces.
3) The time of validation. When we validate, the mailbox might have been active and when you actually sent it might have been inactive or invalid. This is rare but does happen time to time.
4) It could be the IP or provider you are using to send your email campaigns. This happens to be the most obvious one. Some email providers don't have such a great reputation with services like Gmail, Yahoo, or even private email providers. Therefore, any email campaign you send with them could be reject on the basis of their IP being listed in blacklists. This is nothing to do with how valid an email is...its just to do with the IP address or provider you are using to send their email campaigns.
5) It could you email content. Even if we provide you with 100% valid email addresses, if your email content isn't up to scratch, it will bounce back and your message is likely to be rejected by the providers. This is not something we can help you with. We suggest checking your email campaign against solutions like SpamAssassin and adjusting to make it high quality email campaign ready to be delivered without issues.
6) It could be your sending practices. Most providers have set of guidelines that must be followed if you want them to deliver mail to your customers. They are often referred to as bulk sender guidelines. One of the most popular guides is from Gmail. They check your email against things like SPF, DKIM, DMARC, rDNS and others to determine whether they should deliver or reject your email outright. This is again not to do with how valid an email address is but more on if you are following the guidelines for becoming a good sender.
Email Deliverability is a complex subject and involves a lot more things than what we mentioned here. We suggest you get guidance from your provider and from online resources. This will help you achieve better deliverability. Also keep in mind that email verification is to help you eliminate majority of the bounces.
Email Verifier is not a tool which will remove all the email addresses that are likely to bounce. If some of our competitors are promising you that they will get rid of 100% bounces, they are most likely issuing a false statement or sending blank emails (unethical behavior) behind your back.
Even by sending blank emails, they still cannot guarantee you with 100% bounce removal.