Email Hosting Discussions

As more people move from POP3 to IMAP configurations, questions continue to come up about these protocols and their utility in mail client applications. While it is widely accepted that the newer IMAP protocol is better than POP3, a number of factors should be considered before choosing one protocol or the other.

What are these protocols and how do they work in your email applications? Both POP3 and IMAP protocols allow for mail client applications like Outlook and Thunderbird to access mail from a remote server. What distinguishes these protocols from one another is the way each one handles messages on the server.

When a mail client uses POP3 to connect to the server, messages are downloaded from the server to the client mail application. Users may configure their client to download and permanently delete messages from server or to download and leave a copy of the messages on the server for a period of time.

IMAP, on the other hand, does not download messages from the server. Each time a user connects via IMAP, the mail client synchronizes with the server and displays message header information for messages that actually reside on the server. Often, IMAP is described as "working off" the server.

The IMAP concept of working off the server represents a substantial shift from its POP3 predecessor. While POP3 utilizes the mail server to queue and transfer messages, IMAP is truly a server-centric model providing a server side directory structure to which client applications are synchronized.

Server-centric message management is one of the great advantages of IMAP over POP3 and makes possible the concept of a single inbox across multiple clients and webmail. Connecting with IMAP, a user may access the same messages in the same inbox on more than one machine. Similarly, groups accessing a single mailbox may all view the same messages and folder structure.

While POP3 messages are downloaded and deleted from the server, IMAP messages are not removed until an action to delete them is made. IMAP clients generally support a two-step deletion process: 1) Messages are marked for deletion, and 2) Marked messages are permanently purged. Aside from being restored from backup, once a message is purged, it is gone for good. An advantage of IMAP is that a message need not be deleted multiple times as is often the complaint of POP3 users working with copies of downloaded messages on multiple machines and devices.

So why not ditch POP3 entirely and move to IMAP? The major drawback of IMAP is that it requires an internet connection since messages are stored on the server and are not downloaded to the local environment. A second drawback is server storage. Since messages are stored on the server, disk quotas can quickly become an issue with larger mail accounts. Lastly, the time to synchronize to the server is not immediate. Accounts with thousands of messages will experience longer synchronization times than accounts with several hundred messages. Depending on the user’s client and version, IMAP setups may prove impractical with more than several thousand messages as server connections timeout.

IMAP provides an elegant solution for managing mail using multiple machines. However, there is a POP3 workaround allowing users to manage their mail on several devices. By manipulating settings in the POP3 client applications, a user can select to save messages on the server for a specified period of time or until messages are deleted in the client program. In practice, this can allow POP3 users to download and delete messages on the server using different machines.

A drawback to the POP3 workaround is that any sent messages from one machine will not synchronize with other devices. Synchronization of folders including sent mail can only be achieved via IMAP. While not truly server-centric, the POP3 workaround is nevertheless a proven method limiting server storage and lightening server connections.

At Greatmail, all email hosting accounts may be accessed either via POP3 or IMAP. We generally recommend IMAP configurations for users accessing their mail from multiple machines or groups who use one mailbox for a specific task (for example, a support or sales group). However, if users are working from single computers and only use webmail to access new or recent mail, then POP3 is a more than adequate solution.

It should also be noted that IMAP plays an important role in emulating an Exchange-like email experience. Combined with an Outlook Sync plug-in that synchronizes Contacts, Calendars, Notes and Tasks between the server and Outlook, IMAP stands as a highly competitive and cost effective rival to Microsoft Exchange.

Labels: imap, imap_email, pop3, pop3_email