Below this list of links are a set of titles on various topics, each with a set of pointers to their primary related files. For example, the topic of sendmail might have links to the items named aliases, sendmail.cf, sendmail.cw, virtusertable and possibly others. Otherwise, files are assumed to be binary, or of a data format characteristic of a particular system program. This is generally setup at system install time. This is used by sendmail to redirect a destination.
Most systems have aliases for postmaster, webmaster, etc.
Aliases can also be directed to multiple destination mailboxes, or to an entire distribution list. This file is generated by the program newaliases , which builds the index and signals sendmail that there has been an update. If you update aliases, be sure to run newaliases . Refer to the man pages on those programs for a description of this file. This has a slightly different format than the per-user crontab, which simply has a list of runtimes and a program to run.