Signature Links are always helpful for promotion of website if they are relevant. Moreover do follow links give additional benefit to the website for which the links are created
Off Page SEO is link building techniques and white hat SEO is always preferable. Always get links from relative websites and from those websites that have high domain authority ?
These are the techniques that are hated by the Google. This is un-ethical work done by many webmasters. Because of this work websites are often penalized.
Email is type of marketing in which first you create a list and then write a Newsletter and send your message through a software to all of your list members. It is one of the verified way of direct marketing