Read the mail emailpool indexed for one pool address (a `pool+<tag>@…` tag keys a project), oldest first, received at or after `since` and after `after_seq`, with the links each mail holds. The address must be on the calling key's allow-list: any other is refused, not answered empty. No mail yet is an ok with an empty list, so a caller can poll; pass the returned `cursor` as `after_seq` to read on.
Price: $0.00 per unit.
Maximum charge per unit: $0.00.