Internet Message Access Protocol – IMAP
What Is Internet Message Access Protocol (IMAP)?
Internet Message Access Protocol (IMAP) is a protocol used by e-mail servers for the transfers (sending and receiving) of emails.
This protocol allows mail on the server in order to be able to see a different email client or WebMail. It includes advanced features such as multiple mailboxes, the ability to create folders to sort email … The fact that messages are archived on the server that the user can access all their messages from anywhere on the network and the administrator can easily make backup copies.
IMAP uses TCP port 143. IMAP is particularly well suited to access through slow connections. IMAPS (IMAP over SSL) provides secure access to the server using SSL. It uses TCP port 993. The use IMAP over SSL is described in RFC 2595.
Most email clients implement IMAP, since it is widely used by different ISPs.
Free
* KMail
* Mozilla Thunderbird
* Mutt
* Novell Evolution
* Sylpheed
Proprietary:
* Apple Mail
* Lotus Notes
* Microsoft Outlook: poor IMAP support in versions prior to 2007 (unable to delete emails, the emails are not copied to the IMAP mailbox, etc.)..
* Microsoft Outlook Express
* Opera
* Pegasus Mail
* The Bat!
* ContactOffice
Cyrus IMAP
Cyrus IMAP server is the IMAP protocol that implements the most widely used, particularly by ISPs. The software runs as a daemon under environment BSD, Unix or Linux. The main difficulty for the installation of this application is the exclusive use of the command line to manage the accounts, records and access the server.
Other IMAP servers
* Courier-IMAP
* Dovecot
* MDaemon
* Microsoft Exchange Server
* Sun Java System Messaging Server
The other famous protocols are:
The Post Office Protocol (POP)
The Post Office Protocol (POP) is a transmission protocol, through which a client e-mails from an e-mail server. Version 3 (POP3) is described in RFC 1939. POP3 is an ASCII protocol, whereby the management of data is done through commands, the default port 110 to be sent.
A permanent connection to the POP3 mail server is not necessary. The connection to the server is set when needed by the client and is then terminates automatically when not further needed.
POP3 is the very limited functionality and only allows the listing, retrieving and deleting e-mails on the e-mail server. For additional functionality such as hierarchical mailboxes directly at the mail server, access to multiple mailboxes during a session, pre e-mails, etc. as IMAP protocols must be used.
As a counterpart to POP3 for sending e-mails is usually in the clients and servers, the Simple Mail Transfer Protocol (SMTP) is implemented.
POP4
While not yet an official standardized mail protocol, a proposal has been outlined for a POP4 specification, complete with a working server implementation.
The proposed POP4 extension adds basic folder management, multipart message support, as well as message flag management, allowing for a light protocol which supports some popular IMAP features which POP3 currently lacks.
No progress has been observed in the POP4 specification since 2003.
SDPS
Demon Internet introduced extensions to POP3 that allow multiple accounts per domain, and has become known as Standard Dial-up POP3 Service (SDPS). To access each account, the username includes the hostname.
Simple Mail Transfer Protocol (SMTP)
The Simple Mail Transfer Protocol or SMTP is a communications protocol used to transfer electronic mail (email) to the e-mail servers. The SMTP protocol is fairly simple as its name suggests. The sender and the recipient or recipients of a e-mail message are verified for their existence on the internet. After the successful verification, the body of the message is transferred. It is quite easy to test a SMTP server using telnet on port 25.
SMTP is beginning to be widely used in the early 1980s. It is an addition to the UUCP, which is most suitable for the transfer of electronic mail between machines whose interconnection is intermittent. SMTP, on the other hand, works best when the machines that send and receive messages are permanently interconnected.
The Sendmail program is a popular e-mail server that uses the SMTP. As the protocol used the ASCII text (7 bit), it was unable to send any bytes in binary files. To overcome this problem, standards as MIME were developed to code binary files via SMTP. Today, most SMTP servers accept the MIME on 8 bits, which can transfer binary files almost as easily as the plain text. SMTP uses TCP for data transfer.
SMTP does not retrieve remote email arrived in a mailbox on a server. The standard Post Office Protocol (POP) and IMAP has been created for this purpose.
Study:
Wikipedia website
en.wikipedia.org/wiki/Internet_Message_Access_Protocol
en.wikipedia.org/wiki/Simple_Mail_Transfer_Protocol, and related links.
