i received an email with a bunch of bouncebacks. i asked my website host about it and they identified an IP address and advised that if this was mine to check my computer for malware.
If this is due to malware, then you would be the first Mac user to have such an event.
i googled the question as above and got a message that contained an IP address identified as mine. it is the same IP as in the email the website host sent me. the googled page suggest a program called Mackeeper to clear off any malware, viruses etc.
That was almost certainly an ad for MacKeeper as they pay big money for such things and not so much for their product. If you search this Forum, you will find many many unhappy users.
All the spammer needs to have is your e-mail address in order to send such mail out. At worst, they have hacked your e-mail account by guessing the password and used the server to send out these messages. Check your "Sent Mail" folder and if you don't see any of these messages, then they just made it look like it came from you by faking your e-mail address. If you do see those messages, then change your e-mail password to something they can't guess again.