After my domain name provider switched to a new system, ssh'ing into new subdomains that I had created and edited in the (new) dns editor became very very slow.
Turns out, that while the old system did not create new ipv6 fields for a new sub domain, the new system does - and adds the address of the local server.
Apparently ssh first tries ipv6 if available. (I discovered this using the verbose option
ssh -vvv). Only after looking up ipv6 and timing out, it tries ipv4.
So, fill in those AAAA records with the proper ipv6 address!
Note: the record with only @ is domain name proper, without
www or another subdomain.