OT: SPAM Spoofing

I've got a problem, and am wondering if anyone has any advice as to what I can do. I run my own private mailserver on my OpenVMS 7.3-2 system. Only a few people know how to get ahold of me, and it's basically used to communicate with my family. Someone started sending out spam yesterday that appears to be coming from my IP address and domain name based on the email headers, yet I've verfied the messages aren't originating from my network. As a result of this my VMS server has been thrashing, the B******* are using a fake account name that is 14 characters long, so OpenVMS won't automatically reject it, but instead bounces the bounces, then accepts the bounce backs. Last night I finally shut down SMTP on my VMS server, and am blocking all incoming SMTP connections at my firewall. I've also alerted my ISP as to the problem. Is there anything I can do about this? My one thought is to do an "emergency" upgrade to OpenVMS V8.3 as it will reject email to invalid accounts that are 13+ characters in length, and then turn SMTP back on. I've been meaning to do the upgrade, but haven't had time yet. Zane