Sendmail also uses the /etc/aliases file, and the format is the same as that for Exim. However, Sendmail keeps a hashed table file of the contents of /etc/aliases, and you will need to run the "newaliases" command in order for this separate file to be updated after you have edited the original /etc/aliases file. This tends to be the #1 thing that e-mail administrators forget to do on a Sendmail system!

As with Exim, you can use the "mailq" command to view the current mailq, and see what mail is still to be delivered.