Salesforce | How to track email sent by workflows or process builder in email history section of record?

1.Create an email template.
For example, we created a template called “Leads: Welcome email”
Somewhere in the template, add “ref:{Object Id of the record}” which you want to track the activity
For example, in our template, we added ref: {!Lead.Id}. If you want to hide this line than create an html email in first step and using html tags make display line in white color like : ref: {!Lead.Id}
2.Make it send to the recipient as well as to the administrator’s Email-to-Salesforce address.
All emails sent to email-to-salesforce address are saved in history and use ref id for relation with object.