What is the best Java email address validation method?

Apache Commons is generally known as a solid project. Keep in mind, though, you'll still have to send a verification email to the address if you want to ensure it's a real email, and that the owner wants it used on your site.

EDIT: There was a bug where it was too restrictive on domain, causing it to not accept valid emails from new TLDs.

This bug was resolved on 03/Jan/15 02:48 in commons-validator version 1.4.1

If you're looking to verify whether an email address is valid, then VRFY will get you some of the way. I've found it's useful for validating intranet addresses (that is, email addresses for internal sites). However it's less useful for internet mail servers (see the caveats at the top of this page)

What do you want to validate? The email address?

The email address can only be checked for its format conformance. See the standard: RFC2822. Best way to do that is a regular expression. You will never know if really exists without sending an email.

I checked the commons validator. It contains an org.apache.commons.validator.EmailValidator class. Seems to be a good starting point.