Navigate to the Banned emails page.
Admin Control Panel → Users → User discipline → Banned emails
Click on the Import button and select the banned_email_hosts_2018-12-19.xml file that is included in the zip archive.
This list is derived from the MIT-licensed mailchecker by FGRibreau and disposable-email-domains by andreis.
Updates should happen on a once per month basis, maybe less frequently depending on my workload.
The following free domains are blanket banned: .tk .ml .ga .cf .gq
The list was increased from 5,318 hosts to 5,582 in the December update.
All hosts, that are of 5 characters or less, have the @ symbol prepended before the host (appended after the wildcard). Lengthier domains are evaluated without the @ symbol.