How to get warning if there is an e-mail? I know how to set vibration when getting an e-mail: How to set vibration ON when getting e-mail (Gmail)?

But how can I set my Android phone to always vibrate/give sound when getting an e-mail?

I'm asking it because once I get an e-mail, my phone will stay silent, even if I get another e-mail. I need a feature/setting that enables this, to have a warning, when a message arrives.
Uncheck the "Notify Once" option in your GMail account settings and you should get a notification for every new message.

(Specifically: Menu -&gt; More -&gt; Settings -&gt; Notify Once)

Edit: Apparently older versions of GMail do not have this option, in which case you would actually need to try a third-party app such as GMail Notifier.