A PhD advisor usually sent all his letters of recommendation for his students through his secretary. He wrote a letter for his PhD student who is currently applying for academic positions, and unexpectedly died a month after. The secretary has a letter. Should this letter be submitted as a part of application? Should it be stated in the cover letter that the letter is from a deceased advisor and how the submission should be handled (for example, for MathJobs should an account with the secretary email be created)?
The advisor worked in the US and the applicant is considering both American and European universities.