well
your email signature must be tailored depends on the product/campaign and where you'd like your customers to be directed to
example
Website Homepage
- if you are trying to promote your website. by all means put your website's homepage in your email signature.
but be sure your homepage acts like a landing page. this strategy directs your visitors attention to the activity you want them to take.
writing your website's homepage helps to expand awareness of your brand
Social Media
either include a link to your personal accounts on sites such as Google+, Twitter, LinkedIn, Facebook etc.
or you can include links to your company’s accounts. Both are good options.
those are just few options
remember that your email signature does not have to showcase unnecessary info