Is it a good idea to use a subdomain or an entirely different domain name for sending generated emails such as registration, password reset...? So that the main domain doesn't get marked for spam. what about IP addresses?
what are some the pros and cons?
No, this is not necessary. Only if you send bulk mail, but then you're better off handing that to a service provider for sending it out, as they have far more experience in making sure that your e-mail reaches the target mailboxes.
Also, just changing domain/subdomain does usually not work, as BAN's are largely based on IP addresses as well, or only on them.
