Most email services, especially those offered by consumer ISPs, use the old POP3 / SMTP protocols as the backbone for their email services. This works properly when only one computer is working as an email client because there is an expectation for the email to be downloaded off the mail server to that one computer.
Now the reality has changed due to Moore’s Law allowing for the ISP to offer email storage capacity to their customers in the order of gigabytes. As well, the computing paradigm has shifted towards people viewing their email from multiple devices. This has been brought about with small business owners having an office computer and a home computer, as well as the increasing popularity of smartphones, tablet computers and secondary-tier notebook computers like netbooks and 13”-14” ultraportables.
What does IMAP4 offer over POP3?
The IMAP4 technology requires email to be stored on the server and allows a copy of the mail to exist on the client devices. When the email client connects to the IMAP4 server, it simply synchronises all the email between the client and the server. This includes synchronising the client outbox to the server outbox in order to have emails being sent.
There is the ability for an IMAP4 setup to support “header-only” downloading, which would be of importance to people who use portable devices or low-bandwidth connections. As well, an IMAP4 setup can allow the user to operate in “offline” mode where synchronising is done when the user explicitly goes online so that users can prepare their email where Internet access is unavailable but synchronise when it is available.
Compared to POP3 / SMTP, this allows for increased flexibility when it comes to maintaining a mailbox from different email clients. Primarily, the contents of the same mailbox appear in all client devices that can access that mailbox. An example of this benefit would be that the Sent folder contains all messages that are sent from all of the clients rather than from that particular client. Similarly, one could “rough-out” an email using a smartphone or other portable device, then “finish it off” on the desktop because the email will be held in the Drafts mailbox folder.
It also supports the ability to create mailbox folders which will allow you to file the email in a manner that suits you, yet see the same filing arrangement across all your client devices.
It is also worth knowing that IMAP4 is the basic email protocol that OMTP have called as part of their standard for mobile “visual voicemail” services. These services allow a user to manage voicemail that they receive on their mobile phone in a similar manner to how they manage email on their computer or smartphone.
The status quo with IMAP4
IMAP4 is a free open-source technology that is independent of any licensing requirements; and nearly all email clients for desktop and mobile operating environments offer IMAP4 support as standard.
It is even though most of the consumer ISPs don’t offer it as an email protocol to their customers. This is while an increasing number of these providers are now offering mailboxes with gigabyte file capacities to new customers and upsizing existing customers’ mailboxes to these capacities. As well, the current range of data-centre equipment that works as mail servers can handle IMAP4 easily.
Some of these providers would rather offer a “hosted Exchange” service which would require the user to use Microsoft Outlook in Exchange mode. These services are more expensive to provide and may cost more for most personal and small-business users.
What could be done
An Internet service provider could offer IMAP4 mailboxes as a standard option for new customers or customers opening up new mailboxes. As well, they could offer it as a free upgrade option to existing customers, with information on how to convert from POP3 / SMTP to IMAP4.
This kind of setup that IMAP4 offers can allow telcos who offer Internet service and telephony as a bundle or triple-play services to provide a unified messaging environment where customers can manage their voicemail, fax and email from the same terminal. It also opens up ways for these companies to add value to their telephony and Internet services.
It also is a way of supporting the Internet-usage reality which is a reality driven by multiple-computer setups and portable computing.