- Double opt-in. I've talked about double opt-in (aka "confirmed opt-in") many times on this site before, so click on through if you want to read more about how it works. In a nutshell, it is extremely accurate email address validation. Make sure any sort of "welcome" or "confirmation request" message REQUIRES an affirmative response from the recipient before future mailings commence. If you do it as an "opt-out" -- sending a welcome email and telling people they can unsubscribe if they want -- that is NOT double opt-in. That will NOT validate email addresses properly. You will end up with a very dirty list and deliverability problems, to boot.
- Don't buy lists. For some reason, a lot of the people who ask about email address validation are asking because they're buying email addresses and trying to ensure that they're extracting the valid addresses out of what they've bought. YOU'RE DOING IT WRONG. Don't even bother validating these addresses. Feel free to assume that the list is 100% garbage, because it is! List sellers have horrible hygiene. And while some addresses are sure to be "legit," you're a spammer if you mail to them. Those people didn't sign up to receive email from you, and there are no exceptions to be made, regardless of what the list seller will claim.
- Don't reactivate old bounced addresses. Your email service provider (ESP) might have functionality that allows you to reset the status of subscribers, turning them back to "active" after they've been marked as dead by the system after bouncing days, months or years ago. Sure, maybe a few of those got bounced by accident, or due to some transient issue, and would be fine now. The problem is, there's no way to tell which. And any validation process damages your sending reputation. More than 90% of those addresses are for certain still dead, and tickling ISP mail servers trying to find the 10% good ones is just going to cause you to be blocked. Is it really worth the headache?
- Let your list management application or email service provider do it's job. As I mentioned above, most ESPs or list management applications automatically denote which addresses bounce repeatedly, and will mark those addresses as dead. Trust them. Allowing it to weed bounces out of your mailing lists benefits you greatly. Excessive attempts to mail invalidated addresses will cause your sending reputation to suffer.
- Pay attention to interactions and responses. Don't be so focused on perfect validation of every POSSIBLE email address you could be mailing. The email industry has moved on - being sensitive to subscriber engagement is more likely to have a significant impact (be it positive or negative) on your deliverability success. Do you have a subscriber lifecycle management plan in place? Are you focusing on your engaged subscriber base of people who open and/or click on emails? What are you doing with the "emotional unsubscribes" - people who haven't opened or clicked on your emails in many, many months? These are the things you should be thinking about.
Email Address Validation: Options
In my previous post, I talked about why SMTP-based email address validation is a really bad idea. Today, I'll talk about what your options are. You want to validate email addresses properly, so what CAN you do? Here are my top five tips.