Although there are many alternatives to Apache commons, their implementations are rudimentary at best (like Apache commons' implementation itself) and even dead wrong in other cases.
I'd also stay away from so called simple 'non-restrictive' regex; there's no such thing. For example @ is allowed multiple times depending on context, how do you know the required one is there? Simple regex won't understand it, even though the email should be valid. Anything more complex becomes error-prone or even contain hidden performance killers. How are you going to maintain something like this?
The only comprehensive RFC compliant regex based validator I'm aware of is email-rfc2822-validator with its 'refined' regex appropriately named Dragons.java. It supports only the older RFC-2822 spec though, although appropriate enough for modern needs (RFC-5322 updates it in areas already out of scope for daily use cases).
But really what you want is a lexer that properly parses a string and breaks it up into the component structure according to the RFC grammar. EmailValidator4J seems promising in that regard, but is still young and limited.
Another option you have is using a webservice such as Mailgun's battle-tested validation webservice or Mailboxlayer API (just took the first Google results). It is not strictly RFC compliant, but works well enough for modern needs.
