The other thing that can happen is that you have somehow "given away" your email address and password by mistake.
Lets look at how that can happen.
You have an email address of say
[email protected]. The password for the email system is "football".
Then you register for a web site (any web site).
Most web sites nowadays ask you to register for a web site using your email address, so you use
[email protected]. As a password on that web site you use a password of "football".
So by registering for that web site with
[email protected] and using a password of "football", you have given the web site owners the ability to logon to your email system.
Some suggestions:
Have a number of different email addresses and use one ONLY for friends and family, never use it for anything else.
Then create other email addresses for registering for web sites. Use googlemail or hotmail for free email addresses.
Then ALWAYS use a different password for your email system to the one you use for web sites.