NAME
Mail::DKIM2::Split - Bcc-safe recipient grouping before DKIM2 signing
SYNOPSIS
use Mail::DKIM2::Split qw(plan_copies);
my $copies = plan_copies($message_bytes, ['<a@x>', '<b@y>', '<bcc@z>']);
# -> [ { rcpts => ['<a@x>','<b@y>'] }, # disclosed (in To:/Cc:), one copy
# { rcpts => ['<bcc@z>'] } ] # Bcc, its own copyDESCRIPTION
A DKIM2-Signature records the hop's RCPT TO in rt=. Signing one copy of a message to every recipient would put the Bcc recipients in every copy's rt=, where every other recipient can read them. The message has to be split before signing: recipients named in To: or Cc: can share one copy, and each undisclosed recipient gets a copy of their own. This is the grouping logic, with no network in it; the LMTP daemon in the dkim2.com deployment uses it to fan a submission out into per-copy re-injections.
FUNCTIONS
plan_copies($message_bytes, \@envelope_rcpts)
An arrayref of { rcpts => [...] }: one entry for all the disclosed recipients, then one per undisclosed recipient, preserving the envelope strings as given. A recipient not found in To:/Cc: is undisclosed, so a message with neither header yields one copy per recipient.
disclosed_addresses($message_bytes)
A hashref of lowercased addresses named in To: and Cc:.
AUTHOR
Bron Gondwana <brong@fastmailteam.com>
COPYRIGHT AND LICENSE
Copyright (c) 2025-2026 Fastmail Pty Ltd. This is free software; you can redistribute it and/or modify it under the same terms as Perl itself.