After clicking a link in a message, my Hotmail account sent emails to all the people in my address book.The email itself is not present in the Sent folder items. Bizarrely, the problem occurs from my Android smartphone because I haven't used my PC in last two days.Any ideas on how to solve this problem? I've already changed my password.
Hotmail account is automatically sending emails, no evidence in Sent folder 
spam prevention;outlook.com
You should perform a virus scan on your computer.  The chances of a hacker sending random emails on your account is very slim.  More than likely, the link you clicked performed a drive-by download and loaded malware on your computer.  If the malware sent the same link you clicked to all your contacts, you should tell them to immediately scan their computer for viruses if they clicked it.