My short list, which is probably incomplete as I've never done this. I've gone the other way.
Look in these areas, for dependencies. You should be able to query DMVs for the info on all instances. Look for the domain1 name.
- server_principals
- linked servers
- proxies (SQL Agent, xp_cmdshell)
- jobs
- maintenance plans/SSIS packages
- filters in audits/ee sessions/traces
- database owners
- service accounts
- replication items
- database mail