OptionaldefaultRule applied to domains that match no provider. Defaults to a conservative rule that only lowercases the domain and leaves the local part untouched.
OptionallowercaseLowercase the domain. Domains are case-insensitive per RFC 1035, so this
defaults to true. Disabling it is rarely useful but available.
OptionalprovidersAdditional provider rules, or overrides for the built-in providers. Matched by domain; entries here take precedence over the built-ins.
OptionalreplaceIgnore the built-in provider list entirely and use only the providers
supplied in NormalizeOptions.providers. Defaults to false.
Options accepted by the normalization functions.