Is my email account hijacked?

Just checked my email account and found there is a post delivery failure there. Also there appears some other email sent out from my email account.

By clicking the 'post delivery failure' out it seems that someone took my email to send out rubbish advertising mail . Interesting things here is that it was forwarded to 2 expatforum and singaporeexpatforum plus the 'tantongnee(spelling correct?)' and another landlord in Singapore I approached to recently'. However, 2-3 of my friends are sent the exactly the same content email to as well.

I reported to the Hotmail management team for this issue already.

Does anyone ever encounter such thing? Does that mean that email account is hijacked?

Thank you for any input.

It is possible that your email account or your computer has been compromised, but it is also possible for a spammer to spoof an email address without having access to it.`

In situations like this, you should always make sure you run a thorough scan of your computer with an up-to-date antivirus program. If you are accessing your email via webmail, it certainly won't hurt to change your password, either.