What features do you find most useful in a CRM?

Hi All,
We are building CRM project only for SaaS companies.
I would love to your feedback about your existing CRM which is use.
What features do you find most useful in a CRM ?
Thank you.

  1. Email tracking - who opened what
  2. Automatically pulling company and user profile by email
  3. Useful email templates
  4. Online “Book meeting with me”
  5. Prospects tracking (don’t mind a tracking code embedded in a website)