Spam Spam Sausage and Spam

In an average week, I probably get something like 4-5 spam messages. Sometimes more, often less.
Today, however, I log on to my webmail system and find, get this, 21 pages full of spam.
One page contains something like 30 messages, so that would make something like 600 spam messages. Delivered to me tonight.
This almost never happens, so I can only assume that something is going on. The thing is that it's 'delivery failure' messages, so my name isn't in the target list, but it seems to be in the list of senders. Granted, none of the emails actually use my email, they just use my domain.
I can, without a doubt, say that I've never received this much spam at any single moment in time before. It'll be interesting to read the news today and see if other people are experiencing something similar.