I believe someone hacked my email a year or two ago, but only a few emails were sent, but the were sent unsuccessfully. I kept getting messages saying message failed, and I had no idea what it meant. I just changed my password, and the messages stopped.
It happened to me a long time ago. I hadda get my Internet Service Provider to help me get things straightened out. I don't know how many eMails got sent out, and they all contained just a single link, in my case to sexually raunchy sounding addresses. After Siggy started this thread I noticed I've rec'd two such eMails, each from someone different, both of which contain a single link.
Never click on the link, return or forward the eMail. Delete it, then contact the person(s) in your contact list via a separate eMail to let them know they have a hacker.