How to know from which email client the HTTP request was coming from? [duplicate]
问题 This question already has answers here : Closed 8 years ago . Possible Duplicate: Email client detection I have a newsletter which will have a link to my websites pages. Now i want to know which email client (gmail, hotmail, outlook) the user opened the newsletter in and clicked the link to the website page. The reason I want to know which email client, is because i want to customize the content in website pages based on the use of email client by users. My Website pages will be coded in PHP