IMAP History and Standards
The first version of IMAP was formally documented as an internet standard was IMAP version 2,
and in RFC 1064, and was published in July 1988. It was updated in RFC 1176, August 1990,
retaining the same version. So they created a new document of version 3 known as IMAP3. In
RFC 1203, which was published in February 1991. However, IMAP3 was never accepted by the
market place, so people kept using IMAP2. The extension to the protocol was later created called
IMAPbis, which added support for Multipurpose Internet Mail Extensions (MIME) to IMAP.
This was a very important development due to the usefulness of MIME. Despite this, IMAPbis
was never published as an RFC. This may be due to the problems associated with the IMAP3. In
December 1994, IMAP version 4, i.e., IMAP4 was published in two RFCs, i.e., RFC 1730
describing the main protocol and RFC 1731 describing the authentication mechanism for IMAP 4.
IMAP 4 is the current version of IMAP, which is widely used today. It continues to be refined,
and its latest version is actually known as IMAP4rev1 and is defined in RFC 2060. It is most
recently updated in RFC 3501.
IMAP Features
IMAP was designed for a specific purpose that provides a more flexible way of how the user
accesses the mailbox. It can operate in any of the three modes, i.e., online, offline, and
disconnected mode. Out of these, offline and disconnected modes are of interest to most users of
the protocol.
The following are the features of an IMAP protocol:
❖ Access and retrieve mail from remote server: The user can access the mail from the
remote server while retaining the mails in the remote server.
❖ Set message flags: The message flag is set so that the user can keep track of which
message he has already seen.
❖ Manage multiple mailboxes: The user can manage multiple mailboxes and transfer
messages from one mailbox to another. The user can organize them into various categories
for those who are working on various projects.
❖ Determine information prior to downloading: It decides whether to retrieve or not before
downloading the mail from the mail server.
❖ Downloads a portion of a message: It allows you to download the portion of a message,
such as one body part from the mime-multi part. This can be useful when there are large
multimedia files in a short-text element of a message.
❖ Organize mails on the server: In case of POP3, the user is not allowed to manage the mails
on the server. On the other hand, the users can organize the mails on the server according
to their requirements like they can create, delete or rename the mailbox on the server.
❖ Search: Users can search for the contents of the emails.
❖ Check email-header: Users can also check the email-header prior to downloading.
❖ Create hierarchy: Users can also create the folders to organize the mails in a hierarchy.