Why am I sending spam emails and why are all my folders empty in my Yahoo account?

[Ann]

My email account has sent out some spam emails. This morning I received the following email from Yahoo:

Dear User,

Our systems detected an error in your account. We strongly advise you to update your account to avoid suspension or de-activation.

Click on the link below to update and activate your account security.

CLICK HERE

Thank You.
Yahoo ©.

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This looked entirely legitimate so I clicked and confirmed my email address. However I started getting messages from other people by telephone that I was sending out emails about the Ukraine.

I normally log on to my emails through Windows Mail. I have just logged straight on to Yahoo and all the folders are empty! I have sent myself emails from my Google and Virgin account, but they do not come into my Yahoo account except through Windows Mail, even if it is closed down. I have no names in the contact list, although if I start to write an email I can access contacts by putting in their initial letter.