When I worked in a job that generated lots of email and returned after a break, I had the same unpleasant task. But I bet you'll find about 80%-90% of the issues raised in those emails have magically resolved themselves in your absence, or can be resolved simply by forwarding the email to the correct person. The lesson I learnt was to immediately delete 90% of my incoming email from that point on (and 100% of email sent to multiple recipients), without replying. The work still got done, I didn't seem to be particularly out of the loop, and everyone quickly got used to the fact that I rarely bothered to answer email.
It should be said, I was most definitely not cut out to work within that kind of monolithic, large organisation and found a way to safely get out as soon as I could! So apply my tactics at your own peril.