Limit registration to non-disposable email address users

Protection against freemium abuse begins upon signup. Limiting registration to only those who don't use disposable email addresses is one way to do that. You can integrate a bulk email verification API into your registration page or use a disposable email domains database like the one provided by WhoisXML API to automatically check if the email address a subscriber provided is disposable or not. A useful bulk email validation tool would tell your administrator immediately that the address is disposable, and so it's likely you're dealing with someone who might try to abuse a free trial.

Make sure the email address is contactable

Not all freemium abusers use disposable email addresses. Some can just as easily use personal email addresses from Gmail, Yahoo, or other free services. A lot of people keep extra email addresses to direct email marketing or newsletters to. It's one way to keep their primary personal inboxes less crowded.

Since these secondary email addresses probably get tons of marketing collateral each day, they're likely full, and so messages will sooner or later bounce. That's not good for any company as it translates to a high bounce rate, which can adversely affect its email deliverability and domain reputation.

A robust bulk email validation API can instantly let you know if all the email addresses in your contact database are accessible. It tells you if every address is Simple Mail Transfer Protocol (SMTP)-enabled and, therefore, able to receive messages. So, if you, for instance, have the email address soon_be_to_nothing@yahoo.com in your database, which has an email verification result that says it isn't SMTP-reachable, it may be best to take it off your distribution list to lower your bounce rate.

Taking the email address that's probably no longer in use off your subscription list is also advisable. That way, your chances of dealing with a freemium abuser is reduced as well.

Keep your distribution list in tip-top shape

The more unreachable email addresses in your distribution list, the higher the chances of ending up in someone's blacklist. It is, after all, not uncommon for spammers or cybercriminals to use the shotgun approach in attacks. Sending messages to as many inboxes as possible, after all, increases their chances of success. Using their tactic for a legitimate business, however, is unacceptable either. Organizations are not allowed to send emails to just about anyone without their consent.

And so companies that want to stay off blacklists should make it a point to keep their distribution lists updated at all times. But we also know that over time, contact lists can grow to a massive size, making cleanup tedious and time-consuming. The quickest way to keep email databases in tip-top condition is to use a bulk email validation solution. It lets you check up to 50,000 email addresses in one go to make sure that they won't do your domain reputation any harm and cause you to end up on a dreaded blacklist.

Bulk Email Verification API/Lookup can confirm if each email address:

• Has the correct syntax or follows established Internet Engineering Task Force (IETF) standards
• Is not disposable by checking its domain against those of known disposable email providers that include Mailinator, GuerrillaMail, and more than 2,000 others
• Has a corresponding mail server evidenced by properly configured mail exchanger (MX) records
• Points to a valid inbox that lessens your chances of dealing with suspicious users
• Is not associated with a catch-all mailbox that isn't assigned to any particular user and so may not add value to your distribution list

While allowing every potential subscriber to try your product/service free of charge is a great thing, you still need a way to keep the system honest. Strike a balance between keeping free trial abuse to a minimum and encouraging individuals to register for your offerings with the help of bulk email validation solutions.