OptionallowercaseLowercase the local part. Most consumer providers treat the local part case-insensitively, so this is enabled for the built-in providers. The email spec (RFC 5321) technically allows case-sensitive local parts, so it is left disabled for unknown domains by default.
OptionalremoveRemove all dots (.) from the local part. This is Gmail's behavior:
john.doe@gmail.com and johndoe@gmail.com are the same mailbox.
OptionalsubaddressCharacters that begin a "sub-address" (also called plus-addressing or
tagging). Everything from the first occurrence of any separator to the
end of the local part is stripped. Gmail/Outlook/etc. use "+"; Yahoo
historically uses "-".
A separator at index 0 is ignored, because stripping it would leave an empty local part.
The set of transformations that can be applied to the local part of an address. Both ProviderRule and DefaultRule share these fields so the engine can treat a matched provider and a fallback rule uniformly.