Remove a domain

Removes the domain from this project.

The provider identity is torn down only if no other project still uses the same domain — SES identities are account-global, so an unconditional delete would revoke another project's DKIM signing along with yours. Domains that were adopted rather than provisioned by Volanea are never torn down at the provider.

Sends from addresses on this domain start failing as soon as the record is gone. Mail already queued is not recalled.