How did spammers get my e-mail address?

I have used the same e-mail account for 6 years. I do not enter my e-mail address on ANY website. In ten years, I have never had a virus. I keep my virus and mal-ware programs updated and scan my computers every day. I have never received any other spam or junk e-mails to this e-mail address.

For the past two months, I have received spam from wowaccountadmin@blizzard.com about my account being compromised, character transfers requested, etc. I run an authenticator. How did the spammers get my e-mail info, Blizz? Was your e-mail server hacked?

Here's an example of the spam content, which I received this morning:

Our in-game customer service representatives are available around the clock to assist you with all your account needs.
your account can and will be disabled.An email has been sent to the registered address on the account with the reason for this temporary closure. If you would like to appeal this decision or did not receive the message please contact our Account Administration team via our webform.

We need to confirm you are the original owner of the account.
We have the evidence to prove that your account involved in the controversial game currency transaction

To ensure the legitimacy of your account, The investigation will be continued by Blizzard administration to determine the action to be taken against your account.
To ensure the legitimacy of your account.

If you did NOT make any changes to your account or subscription, we recommend you login to Account Management at the following link to review your account settings:

<removing malicious URL>

ETC .. Thanks for you time
Centayne