more 1.2 -> 2.2 hints

[George Robbins]

This one is kind of delayed action:

With Ultrix 2.2, sendmail apparently expects the mail spool directory
to be setup with protection 1777 (see "man 2 chmod").  If you have
a pre-existing spool directory, it is probably set up as mode 755 and
sendmail is unwilling to automatically create mail boxes for new users.

The symptoms are mail being returned with errors like so:

   ----- Transcript of session follows -----
mail: cannot append to /usr/spool/mail/renate
mail: cannot open dead.letter
554 renate... unknown mailer error 1


Adding the "sticky bit" to the directory permissions restricts users from
deleting, renaming or changing the protections of files in the directory
unless they are the "owner" of the file.  Normally a person having write
privledges on the directory can do some of these things.  I belive this
special treatment may also be appropriate for the /tmp and /usr/tmp
directories, basically a matter of how "public" you consider any files/
data in those direcoties.