Personal DMs (Pro)
Signing invites and reminders as private Slack DMs with each person’s own link.
On Pro and up, campaigns that use Slack DMs as their medium deliver invitations, final calls and the celebrant's card as private direct messages — matched to each member by their email address.
Members whose email doesn't match a Slack account simply get email instead; nobody is ever skipped. Personal links never appear in channels — DMs only.