Is there a way how to reveal clients IP address (for sales tracking purposes) by sending him an email? Lets say the client will read the email but will not respond it.
ReadNotify.com - This is the thing you are looking for. It gives you much much more than this. Date and time opened Location of recipient (per their ISP city /town) Map of location (available on paid subscriptions) Recipients IP address Apparent email address of opening (if available) Referrer details (ie; if accessed via web mail etc) URL clicks How long the email was read for How many times your email was opened If your email was forwarded, or opened on a different computer Certified email Ensured-Receipts and retractable emails Invisible tracking Self-Destructing emails Block printing Adobe Acrobat PDF Document Tracking Track MS Word or Excel documents