Unfortunately, there's almost nothing you can do about it, except if you notice that the majority of the original messages that bounced came from the same IP address and you complain to the ISP in question that owns it... but most likely these days they came through some infected botnet which means it's pretty much untracable.
Anyway -- I've been on the receiving end of such a spamflood myself a number of years ago, and we saw this issue pop up a number of times when I worked for an ISP (some unsuspecting customer getting the bounces from some random spammer abusing his domain name in the from: of a spamflood)
On the bright side (if there is such a thing), I've never seen this last more than a week, most likely it will stop any moment now if it hasn't already.
Kind of sucks, but since the email protocols allow anyone to put whatever they want in the from: lines without any form of authentication, there's absolutely nothing you can do to prevent someone from the other side of the planet from exactly doing so.
Anyway -- I've been on the receiving end of such a spamflood myself a number of years ago, and we saw this issue pop up a number of times when I worked for an ISP (some unsuspecting customer getting the bounces from some random spammer abusing his domain name in the from: of a spamflood)
On the bright side (if there is such a thing), I've never seen this last more than a week, most likely it will stop any moment now if it hasn't already.
Kind of sucks, but since the email protocols allow anyone to put whatever they want in the from: lines without any form of authentication, there's absolutely nothing you can do to prevent someone from the other side of the planet from exactly doing so.