This may be a special case of 'back-scatter' ? If so, your email address is being forged to send spam to lots of businesses -- because it's the weekend, these are generating the out-of-office messages that are being sent to you. It may be worth checking that your computer is not actually being used to send spam -- do a scan for trojans, etc. Otherwise, the only cure for 'back-scatter' is patience -- it tends to die out in a few days.
HTH
Chris
