I gave my two-week notice last week and I'm spending this week finishing projects, writing documentation, and passing off some stuff for after I'm gone. Part of my work is sysadmin and we have shitty practices on purpose, so there's a ton of stuff that's registered to my work email, or just has one-off passwords, or there's stuff that only I know/have access to. There's a senior sysadmin guy here who's acting really offended that I would quit, and he hasn't spoken to me since I gave my notice, he doesn't respond to my emails, he ignores me when I go to his office and speak to him. We had a bigger meeting last week with my manager and some other coworkers, and the only thing he would say is that I specifically shouldn't make documentation, and pretended he didn't hear me for every other question. No one else acted like that was weird.
My work email is what registered all our machines to the network, so after it's gone no one will be able to get online or access our network fileshare. It's also what's used as our account license for our backup software, so that will stop working if it's not changed. Our website will also go down once my work email disappears. I'm the only one who knows the Windows domain admin password - he won't be able to administer it if I leave and it's not documented.
What's the most responsible/professional way to deal with this?