One of your accounts may be spamming. At any rate. Post the email here, or just the part with the ip address and it can be traced back, to see if it really is from you. If it is, you must find the account and remove it. If not from you, you need to forward a email of it to the person responsible.
This is normal happens every other week/month with me
If you know the specific email address, block it. Do not waste your time on spammers. If you just need to vent a bit, process the spam through www.spamcop.net and it will send the abuse report to the parties involved.