Etc hosts sendmail
A blast from the past!
etc/hosts
and sendmail
are two separate components that were commonly used together in the past, but are now largely obsolete.
etc/hosts
:
etc/hosts
is a file that contains a list of IP addresses and their corresponding hostnames. It's a simple text file that maps IP addresses to hostnames, allowing systems to resolve hostnames to IP addresses. This file is typically used by the gethostbyname()
and gethostbyaddr()
functions in C programming.
In the past, etc/hosts
was used to resolve hostnames to IP addresses, especially when DNS (Domain Name System) was not available or was not functioning properly. The file was maintained by system administrators to ensure that local hosts could communicate with each other.
sendmail
:
sendmail
is a mail transfer agent (MTA) that was widely used in the past to send and receive email. It's a program that reads email messages from a queue, looks up the recipient's email address, and forwards the message to the recipient's mail server.
In the past, sendmail
was used to send and receive email between systems. It was responsible for routing email messages between mail servers and delivering them to users' mailboxes.
How they were used together:
In the past, etc/hosts
and sendmail
were used together to enable email communication between systems. When a user sent an email using a mail client, the email was sent to the local sendmail
daemon, which would look up the recipient's email address in the etc/hosts
file to determine the recipient's mail server. The sendmail
daemon would then forward the email message to the recipient's mail server, which would deliver the message to the recipient's mailbox.
Why they're no longer used together:
With the advent of modern email systems and the widespread use of DNS, etc/hosts
and sendmail
are no longer used together as much. Modern email systems use DNS to resolve hostnames to IP addresses, and email messages are typically sent using more advanced protocols like SMTP (Simple Mail Transfer Protocol) and SPF (Sender Policy Framework).
In addition, many modern operating systems have replaced sendmail
with more modern and secure email systems, such as Postfix, Exim, or OpenSMTPD. These systems use more advanced features like authentication, encryption, and spam filtering to ensure the secure and reliable delivery of email messages.
In summary, while etc/hosts
and sendmail
were once used together to enable email communication between systems, they are no longer used together as much due to the advancement of modern email systems and the widespread use of DNS.