Maybe my explanation is confusing. What I mean is not a 301 redirect in the htaccess, but directly link all domains at DNS level, so we can stop all those separate hostings at a certain time.
All domain registrars have an option to point the registered site to a specific web host provider’s domain name such as ns1.linode.com, ns2.linode.com, etc
Edit:
Blog from my current web host provider…
[offtopic]
One of my registered sites has had the DNS changed to six web host providers. Please note the change is not instant and propagation can take up to about three days to reset all the main global routers.
You can’t redirect on a DNS level. Maybe your provider makes it look like you can, but there is no such thing.
Also, referrers might be used, but they are instable at best and I would recommend against them.
Instead I would suggest .htaccess files on the domains (this may be on a new server, you don’t have to keep the old servers for this) that redirects to the new website with some sort of marker of where they originally wanted to go, e.g.