Mail server

A mail server is a computer network application located on an Internet server, to provide electronic mail service (e-mail or e-mail). By default, the standard protocol for transferring mail between servers is Simple Mail Transfer Protocol (SMTP).). It is defined in RFC 2821 and is an official Internet standard.

The Mail Transfer Agent (MTA) has several ways of communicating with other mail servers using SMTP:

1. Receive messages from another MTA. It acts as a "server" of other servers.
2. Send the messages to another MTA. It acts as a "client" of other servers.
3. Acts as an intermediary between a Mail Submission Agent and another MTA.

Some mail solutions that include an MTA are: Sendmail, qmail, Postfix, Exim, Mdaemon, Mercury Mail Transport System, Lotus Notes and Microsoft Exchange Server and Gmail and Hotmail.

Mail Exchange

A mail server performs a series of processes that have the purpose of transporting information between different users.

Usually the purpose of sending an email is for a user (sender) to create an email and send it to another (recipient). This action typically has five steps:

1. The initial user creates an "email", a file that meets the standards of an e-mail. It will use an application ad-hoc. Some of the most used email-e client applications, in indistinct order are:
   • Lotus Notes (IBM),
   • Microsoft Outlook,
   • Mozilla Thunderbird (Mozilla Foundation),
   • Outlook Express (Microsoft),
   • Windows Mail Desktop (Microsoft),
   • Gmail (Google).
2. The file created is sent to a warehouse, managed by the local mail server to the mail sender user, where a shipping request is generated.
3. The local MTA service to the initial user recovers this file and initiates the negotiation with the recipient's server for the sending of it.
4. The recipient's server corroborates the operation and receives the mail message, depositing it in the "good" corresponding to the recipient user of the mail. The "good" is nothing but a record in a database.
5. Finally, the mail-receiver client software recovers this file or "correo" from the server by storing a copy in the database of the email client program, located on the client's computer that receives the mail.

Unlike a classic postal service, which receives a single package and transports it from one place to another, the e-mail service copies the information corresponding to the e-mail several times.

This process, which in real life occurs very quickly, involves many protocols. For example, to locate the destination server, the Domain Name System (DNS) service is used, which reports a special type of record for mail servers or MX record (Mail eXchange record). Once located, to get messages from the receiving mail server, users use mail clients that use Post Office Protocol (POP3) or Internet Message Access Protocol (IMAP) to retrieve email messages. from the server and store them on your local computers.

Secure or insecure

If you take process into account, there is at least one copy of the mail on the sending server and another copy on the receiving server.

The operating policies of each server, with or without notice to the sending and/or recipient users, could:

1. Receive mails according to some parameter.
2. Do not destroy copies of emails, for example, by successfully transferring them.
3. Copy the emails to any other record or file.
4. Send one or more copies to other recipients.
5. Never destroy the mails stored.

It is extremely important to consider which entity, institution and official are ultimately responsible for managing the mail servers that each one uses. In many cases, emails can be a source of invasion of privacy.

Webmail servers (webmail)

A special form of mail server is one that is accessed via the web using the Hypertext Transfer Protocol (HTTP).

It's not actually a server, but a mail client running on a web server.

MTA Software List