How do email list cleaning companies clean millions of emails daily and avoid being blocked?
Summary
What email marketers say10Marketer opinions
Email marketer from LinkedIn answers that cleaning an email list is an automated procedure. Using sophisticated software, list cleaning companies employ a variety of approaches. One tactic is to perform a syntax check and fix any faults (for example, taking out spaces and special characters). Other tactics check to see if a legitimate MX record exists for the domain.
Email marketer from NeverBounce.com explains that one way email list cleaning companies clean millions of emails daily is through their Bounce Verification technology. It analyzes a mail server's response and determines whether or not it is bouncing. With this the software doesn't count as spam or being blocked.
Email marketer from Reddit explains that some list cleaning services maintain large databases of known spam traps and invalid addresses. They cross-reference submitted lists against these databases to identify and remove risky emails. This is a passive technique that doesn't involve sending any emails, reducing the risk of being blocked.
Email marketer from EmailStuff forum shares Email list cleaning companies use a combination of techniques. This includes Syntax Verification and SMTP Verification to prevent any risk of being blocked. This can quickly get rid of emails from the list.
Email marketer from StackExchange responds that Email List Cleaning companies also use greylisting and temporary failures. This means they will temporarily fail the emails on the first connection to verify it's a real server and not a bot. This allows them to verify an email without the risk of it being flagged as spam.
Email marketer from Validity.com explains that email list cleaning companies use various methods including syntax checks to identify malformed addresses, domain checks to ensure the domain exists and is active, and role-based address detection to flag generic addresses like sales@ or info@ that may be problematic. They also use honeypot detection to identify addresses that are only used to catch spammers.
Email marketer from EmailHippo.com responds that to avoid being blocked, list cleaning companies spread their validation requests across numerous IPs and throttle their connection rates to avoid overwhelming mail servers and triggering abuse detection systems. They also monitor blacklists and adjust their sending behavior accordingly.
Email marketer from Email Geeks shares that in the early days list cleaning companies tried to deliver to the addresses and then drop the connection once the recipient was accepted, but that got them blocked frequently. So most of them these days use data analytics on their entire data set to work out the probability of an address being valid. It's a pretty murky world, full of scammers and data theft, and not legal in every jurisdiction.
Email marketer from Medium explains a simple technique for ensuring that recipients provided you with accurate email addresses: double opt-in. That is, individuals can register for your email list on one form, but you must send them a confirmation email asking them to validate their email address before they can join.
Email marketer from ZeroBounce.net shares that email validation services connect to mail servers to verify the existence of mailboxes without sending an actual email. This involves checking the SMTP connection and simulating sending a message to see if the server accepts it. If the server rejects the connection, it's an invalid email. This is done at scale to clean millions of addresses daily.
What the experts say6Expert opinions
Expert from Email Geeks answers that the list cleaning companies that do SMTP tickling do get blocked. One approached her around a decade ago to help them bypass filters, their system at that time was to basically snowshoe IPs and domains to try and avoid the blocks that the ISPs put up.
Expert from Email Geeks explains that there are no legitimate “list cleaning companies”, so the first approach is just to lie about their effectiveness. The next is to acquire lists of addresses that bounce and more legitimate services buy or trade data about whether an email address delivers from other senders. There are still bottom of the barrel scam companies that do test via attempted delivery, I’m sure, but the accuracy of that is terrible because they get blocked which means that valid email addresses bounce when they try and deliver to them.
Expert from Email Geeks explains list hygiene is trying to bandage the wound and you're better served trying to avoid getting wounded in the first place by focusing on acquisition through things like double entry email, clear value to customer and corrections on typos in forms and that if you have done all that and still want to do some validation on your audience, my vote is for Kickbox.
Expert from Email Geeks recommends kickbox, being the only player in the space that she will recommend and that’s after Jack spent a lot of time talking to me about their philosophy and anti-abuse approach.
Expert from Spam Resource explains that list cleaning effectiveness varies. It depends a great deal on the source of your list and how long you've had it. Cleaning does not fix a purchased list, or a list that's more than a year old. List cleaning is really most useful if you have a list of current customers or recent opt-ins from your website.
Expert from Word to the Wise responds that one of the reasons email list cleaning companies get blocked is that they are generating traffic that looks like spam. One of the common ways they validate an email address is by sending a ping which is a basic network utility. A ping sends a small packet of data to a specific IP address and requests a response. If the target IP address is active, it will send a reply back to the source IP address. However, the target IP address can prevent any risks of being spammed by not responding.
What the documentation says3Technical articles
Documentation from Mailgun shares that real-time email verification uses sophisticated techniques such as role-based account detection, disposable email detection, and typo correction to determine whether an email address is valid. By using these techniques, they do not have to send emails and therefore prevent issues.
Documentation from Kickbox explains that Email Verification tools look at the domain name of an email for example @gmail.com, and check the DNS records to ensure the domain exits and is active. This can quickly detect invalid or parked domains, and prevent being blocked.
Documentation from SparkPost explains that list hygiene services often verify email addresses by sending a 'silent ping' or using sophisticated algorithms to predict deliverability without actually sending an email that could trigger spam traps. This minimizes the risk of being blocked while still identifying invalid or risky addresses.