merlyn says please stop encouraging DaWolf - he's heading down a dangerous path

It's true that you're heading down a dangerous path. Whatever regex you finally come up with, please don't use it in a production application. Use Email::Valid on the server and don't try to do complex processing in JavaScript.

What is the application you want to validate e-mail addresses for? Do you only care that they're syntactically valid or do you want to verify that there's a real person on the other end? In the second case you'll need to do more than just run the address through Email::Valid.

For educational purposes only, I'll point out that your regex rejects 'er_galvao_abbott@somedomain.com' and accepts 'er...galvao...abbott-_-_-_@somedomain.com'. Is that what you want?