Enviar, receber e organizar e-mails no Outlook.com
Hello
I am sorry for your loss.
Unfortunately, you cannot go through the account recovery process on behalf of another person.
Support cannot simply take the death certificate and grant you access either. It is a legal process you will need to go through. Please check this document: https://support.microsoft.com/en-us/accounts-billing/manage/accessing-outlook-com-onedrive-and-other-microsoft-services-when-someone-has-died
Microsoft must first be formally served with a valid subpoena or court order. Depends on where you live, this particular process can be slightly different from country to country.