Okay, so which domain should I use for paypal and which one should I use for subscribing newsletters?
Whatever you want.
I have a gmail account I use for just about everything, forum contact, WhoIs information, newsletter, etc.. (it has great spam protection).
But, I also have a seperate email for business contacts (though one of my domains) and an unpublished email address just for a registrar contact.
(This is not including about a dozen or so email addresses that I have for web projects).
But also, everything is only as secure as your email. Make your passwords good. TordB would be a bad password for you but T0rdB (the number 0 instead of a the letter o) would be better, to really throw off potential hackers, put something odd in the middle or someplace unexpected. T0?rdB for example. If they allow internation characters, then try T?0rdÃ