The software basics
First, your e-mail server must be Internet-mail capable. That means, at the least, it should support Post Office Protocol (POP) and Simple Mail Transfer Protocol (SMTP). If your customers intend to use PCs in the office and laptops on the road, Internet Mail Access Protocol (IMAP) is a must. With IMAP, mail resides on the server so a user doesn't have to waste time transferring messages from one machine to another. Other popular mail protocols, like Microsoft's Messaging Application Programming Interface or Lotus' Vendor-Independent Messaging, are next to useless for Web mail hosting purposes.
A modern mail server also should be Web-mail capable. While host-based Web e-mail is almost always slower than a POP/SMTP server-client combination, the fact that you can check mail from any Web-connected device makes it wildly popular.
To use Web mail safely, though, you must take extra care on both the server and client side. At a minimum, the Web server should support 40-bit Secure Sockets Layer for e-mail connections. IMAP's host-based message storing also helps ensure that valuable messages aren't left behind on public access PCs. But none of that will help if the user doesn't understand that he must clear any public Web browser's cache after reading mail, lest the next user can easily read his last messages.
For hosting purposes, virtual mail domains also are a must. With that ability, a single mail server can handle the messaging load for multiple domains. For example, with iPlanet Messaging Server you can set up such e-mail domains as accounting.bigcompany.com and marketing.bigcompany.com without the expense of additional server software or registering new domains.
One thing that's new, however, is the growing demand for wireless e-mail capability. The popularity of Blackberry handheld devices, which offer wireless e-mail, proves that customers aren't willing to wait for a winner to be declared in the standards battle between Wireless Access Protocol (WAP) and i-Mode. So make sure the e-mail server you choose supports wireless devices.
