Email by IMAP (Internet Message Access Protocol) is one of the two main forms of retrieving email from an email server. With IMAP mail, email messages are sent to a server. When a popular email client like Outlook or Thunderbird accesses the server, it downloads a copy of the email but leaves the original on the server.

This is different from the other major email protocol, POP3 (the Post Office Protocol version 3), which removes the email after downloading. The fact that IMAP leaves messages on the server is ideal for people who have to check their email from multiple computers or from a mobile device. There are several advantages and disadvantages to this approach:

1. Email from IMAP servers is not removed when it is accessed so it can be downloaded by multiple clients
2. In many cases, business email with IMAP is more reliable because if one device fails or is lost, the email can still be retrieved.
3. Email through IMAP, however, is less secure since multiple copies of the email exist on many different devices.

Still, in most cases the usability of IMAP hosting is such that it outweighs the security issue. If you think email and IMAP are right for your organization, consider these steps:

Action Steps
The best contacts and resources to help you get it done

Find companies that offer IMAP hosting

If you are interested in IMAP and SMTP (Simple Mail Transfer Protocol) hosting but do not have the IT staff to maintain an email server, there are several companies that offer outsourced email hosting. These companies can meet all your POP3, IMAP, and SMTP hosting needs.

I recommend: Two good hosts with lots of options are Runbox, which also offers web hosting, and MailStreet from Apptix, which offers a number of additional business email features.

Consider hosting your own email IMAP servers

All of the major email servers support IMAP functionality. So if IMAP is something you want for your business, install a major email engine and you will have access to all the IMAP features you want.

I recommend: If you have a Windows platform, purchase and install Microsoft Exchange. There is perhaps no better email hosting server in the world. If you are running non-Microsoft servers, install SendMail, which is good but has fewer extra features than Exchange.

On the client side, consider Outlook IMAP plug-ins or configuration

Even without being paired with Exchange, many people use Outlook as their email program because it is user friendly and integrates well with other Microsoft programs. However, Outlook does not handle IMAP nearly as well as it handles POP3. Still, there are ways around it.

I recommend: Look at an Outlook IMAP plug-in like Bynari's InsightConnector, which allows Outlook IMAP to work like Exchange. Also, if you find that your IMAP connection to certain websites (like Google) is not functioning as you would like, consider this IMAP information from Digital Inspiration, which shows how to make Outlook perform faster when connecting to Gmail.

Tips & Tactics

Helpful advice for making the most of this Guide

• •  Without IMAP, webmail is less valuable unless it is the only way email is accessed. Even in the cases of POP3 servers, webmail is normally read directly from the email server; but if another client downloads and deletes the email, the webmail client will not be able to read it.
• •  Instead of IMAP, POP3 servers can be configured to leave an email on the server for a period of time before it is removed.
• •  By default, most mobile applications use IMAP instead of POP3.