There are two email protocols currently available to Imajayne clients for accessing email via a mail program.
POP3
POP is short for Post Office Protocol.
POP3 does not coordinate with the server. Messages marked as read/deleted/replied to in the mail application will not show up as such on the server. This means that future mail downloads with POP3 will show all messages as unread.
It is the best option for simple download and delete email requirements to a single computer.
Comparison to IMAP
- POP is a much simpler protocol, making implementation easier
- POP mail moves the message from the email server onto your local computer, although there is usually an option to leave the messages on the email server as well.
- IMAP defaults to leaving the message on the email server, simply downloading a local copy.
- POP treats the mailbox as one store, and has no concept of folders
- An IMAP client performs complex queries, asking the server for headers, or the bodies of specified messages, or to search for messages meeting certain criteria. Messages in the mail repository can be marked with various status flags (e.g. “deleted” or “answered”) and they stay in the repository until explicitly removed by the user –which may not be until a later session. In short: IMAP is designed to permit manipulation of remote mailboxes as if they were local. Depending on the IMAP client implementation and the mail architecture desired by the system manager, the user may save messages directly on the client machine, or save them on the server, or be given the choice of doing either.
- The POP protocol requires the currently connected client to be the only client connected to the mailbox. In contrast, the IMAP protocol specifically allows simultaneous access by multiple clients and provides mechanisms for clients to detect changes made to the mailbox by other, concurrently connected, clients. See for example RFC3501 section 5.2 which specifically cites “simultaneous access to the same mailbox by multiple agents” as an example.
- When POP retrieves a message, it receives all parts of it, whereas the IMAP4 protocol allows clients to retrieve any of the individual MIME parts separately – for example retrieving the plain text without retrieving attached files.
- IMAP supports flags on the server to keep track of message state: for example, whether or not the message has been read, replied to, or deleted.
IMAP
IMAP is short for Internet Message Access Protocol.
IMAP email access coordinates between the server and your mail application. Messages that have been read/deleted/replied to will show up as such, both on the server and in the mail application.
It is the best option for several people accessing the same email address or accessing your email across several devices (computer, phone, tablet etc)
Advantages over POP
- Connected and disconnected modes of operation: When using POP, clients typically connect to the e-mail server briefly, only as long as it takes to download new messages. When using IMAP4, clients often stay connected as long as the user interface is active and download message content on demand. For users with many or large messages, this IMAP4 usage pattern can result in faster response times.
- Multiple clients simultaneously connected to the same mailbox: The POP protocol requires the currently connected client to be the only client connected to the mailbox. In contrast, the IMAP protocol specifically allows simultaneous access by multiple clients and provides mechanisms for clients to detect changes made to the mailbox by other, concurrently connected, clients. See for example RFC3501 section 5.2 which specifically cites “simultaneous access to the same mailbox by multiple agents” as an example.
- Access to MIME message parts and partial fetch: Usually all Internet e-mail is transmitted in MIME format, allowing messages to have a tree structure where the leaf nodes are any of a variety of single part content types and the non-leaf nodes are any of a variety of multipart types. The IMAP4 protocol allows clients to retrieve any of the individual MIME parts separately and also to retrieve portions of either individual parts or the entire message. These mechanisms allow clients to retrieve the text portion of a message without retrieving attached files or to stream content as it is being fetched.
- Message state information: Through the use of flags defined in the IMAP4 protocol, clients can keep track of message state: for example, whether or not the message has been read, replied to, or deleted. These flags are stored on the server, so different clients accessing the same mailbox at different times can detect state changes made by other clients. POP provides no mechanism for clients to store such state information on the server so if a single user accesses a mailbox with two different POP clients (at different times), state information—such as whether a message has been accessed—cannot be synchronized between the clients. The IMAP4 protocol supports both predefined system flags and client-defined keywords. System flags indicate state information such as whether a message has been read. Keywords, which are not supported by all IMAP servers, allow messages to be given one or more tags whose meaning is up to the client. IMAP keywords should not be confused with proprietary labels of web-based e-mail services which are sometimes translated into IMAP folders by the corresponding proprietary servers.
- Multiple mailboxes on the server: IMAP4 clients can create, rename, and/or delete mailboxes (usually presented to the user as folders) on the server, and copy messages between mailboxes. Multiple mailbox support also allows servers to provide access to shared and public folders. The IMAP4 Access Control List (ACL) Extension (RFC 4314) may be used to regulate access rights.
Server-side searches: IMAP4 provides a mechanism for a client to ask the server to search for messages meeting a variety of criteria. This mechanism avoids requiring clients to download every message in the mailbox in order to perform these searches. - Built-in extension mechanism: Reflecting the experience of earlier Internet protocols, IMAP4 defines an explicit mechanism by which it may be extended. Many IMAP4 extensions to the base protocol have been proposed and are in common use. IMAP2bis did not have an extension mechanism, and POP now has one defined by RFC 2449.
Summary
In summary, if you are just using one computer to access your email and you just want to download it to read, store in a folder or delete it…..choose the POP3 protocol.
If you plan to access your email on several devices like a laptop, a second laptop, smart phone, tablet etc…..then you need to choose IMAP.
