3.21 Why do I get the error message unable to write /etc/mail/sendmail.pid?

Sendmail checks to see if it has write access to the directory in which it wants to create a file without granting special privileges to 'root'. To have sendmail run properly, the directories /etc, /etc/mail, and/or /var/run should be owned by root and be writable by its owner. See question 3.15 for a list of all of the required permissions.