I created event registration web sites (you can imagine something like <http://www.eventbrite.com/>), which allow users to subscribe for event updates. When subscribed, we send mass emails (with the same content) to those users. 

It was ok before, but recently I noticed that GMail always put the email into Spam folder.
As any texts would always go to Spam folder, I suspect that my domain was blacklisted by Gmail.

1) Is there a way to request google to put my domain into the whitelist?

2) Let's say it can't and I decide to register for new domain. 
Is there a way to avoid the mass email to be marked as spam by Gmail? (may be something like what Facebook email notification do?)