An example is iName . As for outgoing mail, in the past one could send it via the SMTP server of such service providers, but things are changing and access to SMTP servers is no longer advertized. That address can be easily changed later on when you change the ISP or move to Jamaica. The best way to check if it happens in your particular case is to send a message to yourself or your friend.
Some mail programs are able to include special headers into outgoing messages.
This problem can be easily handled, just make sure your mail program doesn't reply to such messages without your confirmation. When included in a message it requests a delivery confirmation from your ISP's mail server rather than personally from you, which is out of your control. In other words your primary e-mail address becomes known to the person who included such header in his message. Below is the example of the delivery confirmation automatically generated by the mail server. There are two possible solutions to this problem.