Yopmail allows you to create an email address of your choice. This address is of the form: email@example.com. But for that, you do not need to create an account!
You provide said address to the sites that request it when you register, and if you want to see the e-mails received, you find them at the public address: www.yopmail.com/?monadresse or with the Firefox plugin available here. E-mails remain accessible five days before being destroyed. From these addresses, you can create as many as you want. Plus, these email boxes have an RSS feed and most importantly, Yopmail is free! Of course, these e-mails are accessible by anyone entering the myaddress in Yopmail, so we must make this tool only a thoughtful use. So if you receive an email containing your credentials, delete it once memorized, so no one will be able to log into your account! Once you are sure that the site to which you registered does not send you spam, change your email address by putting the real one. Another thing: first check that the single address you have chosen is not already taken by someone else, this will allow you to differentiate whether the spams comes from the site to which you registered and not the one of the other person! On the other hand, Yopmail does not allow to send e-mails but simply to receive them. What makes Yopmail belongs to this family of tools that many appreciate: the tools that make only one thing but that do it well! Following the commentary of Sofia: it is true that Yopmail is sometimes blocked during registrations, well, know that they have foreseen this case: on the homepage, you have this:
In case Yopmail is blocked, you just need to replace the address firstname.lastname@example.org by myaddress @ UN-des-domains-alternatives-de-yopmail. You have permanent and temporary areas. Generally, those blocking yopmail addresses only block the yopmail.com domain, so others are generally accepted. And to check your mails, no matter the domain (yopmail or one of its alternatives), there is nothing that changes for you!