Google mail or Gmail recently enabled support for IMAP or Internet Message Access Protocol and allows you to access your Gmail emails from other clients, like Outlook or Thunderbird.
Unlike POP, IMAP offers two-way communication between your web Gmail and your email client(s). This means when you log in to Gmail using a web browser, actions you perform on email clients and mobile devices (ex: putting mail in a ’work’ folder) will instantly and automatically appear in Gmail (ex: it will already have a ’work’ label on that email).
In addition, IMAP provides a better method to access your mail from multiple devices. If you check your email at work, on your mobile phone, and again at home, IMAP ensures that new mail is accessible from any device at any given time.
But it seems not everyone has their IMAP activated in their Gmail accounts. Nevertheless the said feature will be rolled out completely in the coming days.