Earlier quoted context omitted.
That this could happen in any organization is surprising. That it happened in IBM is downright shocking. How do you fail an email migration and not have email for your employees? How do you let this affect billing and invoices? Why haven't they at least set up something temporary?
Why haven't they at least set up something temporary? Yes, just spin up e-mail addresses for 400,000 people in 177 countries. No problem. Just run it on a Raspberry Pi in the basement.
Focus on the core business competencies, of which email is clearly not one.
Edit since I can't reply: An extended email outage isn't a good look either. If IBM can't run their own critical systems, why trust them with yours? I personally think making the strategic decision to outsource demonstrates the ability and desire to find timely solutions.