A self-organized project team is sharing facilitator responsibilities, with each person on the core team...

In PMP terms, this question belongs to the People domain because it focuses on team accountability, shared ownership, collaboration, and leadership within a self-organizing environment. PMI’s PMP Examination Content Outline places emphasis on empowering team members and stakeholders and supporting team task accountability. In a self-organized or decentralized team, responsibilities may rotate among members, but the team retains collective accountability for delivery and communication outcomes.

Although the facilitator who missed the email made the immediate error, PMP-style thinking distinguishes between individual mistake and overall accountability model. In agile and self-managed teams, the team owns the process and the result together. The sponsor does not become accountable simply for approving the operating model, and a working agreement is a guide, not an accountable entity. Therefore, the best answer is that the team as a whole is accountable. Afterward, the team should inspect the root cause, update working agreements or communication controls, and improve how client communications are monitored to prevent recurrence.