You have to love free online tools, especially if they aren’t for critical projects. I hesitate to use free tools for essential items, but these are pretty darn good. You should tinker with them if you have some elbow room.
This is a receipt on steroids. Need to know if someone (press, client, blogger, etc.) received an email you sent? Use this tool.
Write your email, hop over to SpyPig, and enter a message title and your email address. Next, pick an image, and copy and paste it into your email. (You can create an account to upload your own image, which means you can disguise it as a social network icon.) You’ll get a notification the first five times the email is opened. This includes when you open it yourself.
Bonus: SpyPig gives you information on the client, his IP address, and the system he used to open the email so you can determine if he read the email while mobile, at the computer, etc.
The downside is if you are an untrusted sender and images don’t automatically open on the recipient’s end, it won’t work.