that would be from then-CEO Neal Patterson,
from Wikipedia :
Patterson is infamous for an email[7] scolding managers for not coming to work before 8 am and leaving before 5 pm, now a prominent example used when discussing email netiquette. On the day that the email was posted to Yahoo!, the company's market cap fell by over 22%[8] from a high of US$1.5 billion.[9]
[7] "BBC News - AMERICAS - Boss's e-mail bites back". BBC. Archived from the original on February 8, 2009.
[8] ..
[9] Flynn, Nancy; Kahn, Randolph (2003). E-mail Rules: A Business Guide to Managing Policies, Security, and Legal Issues for E-mail and Digital Communication. AMACOM Div American Mgmt Assn. p. 45. ISBN 9780814471883. netiquette.
https://en.wikipedia.org/wiki/Neal_Patterson