Sharded email at provisioning stage depends on RP about fedcm HOT 1 CLOSED

Adding to this, the sharded / directed e-mail claim feature requires clarification in general (the privacy goal is clear) (https://code.sgo.to/WebID/#directed-basic-profile)

• given RPs use e-mail addresses to communicate out-of-band with users, who is responsible for generating the addresses and proxying these messages?
• It seems hardly achievable to build a proper setup for this without the IdP supporting this type of directed e-mail natively including the e-mail proxy/forwarding features (as @davidben mentions, user won't be interested / or recognise these directed e-mails)
• making this a mandatory requirement is a really high bar in terms of effort for IDPs, more so because they might not all be e-mail service providers themselves.
• Even if the IdP would be willing to support it, it would be hard to achieve if the IdP is not also in direct control of the top-level e-mail domain (security consideration, address conflicts, ....). They could off course use a dedicated proxy domain only for that purpose, but that seems way beyond the idea of just changing a JS-side integration.
• There seems to be a lot to consider to make this happen, given the e-mail is used for a lot of scenarios specifically also account recovery etc.

from fedcm.