Contracting an ISP
Because your company intranet uses the same TCP/IP standards as the Internet at large, messaging is a wonderfully robust technology that works from the next continent as easily as from the next cubicle.
Particularly among SMEs, a common approach is to contract with an Internet Service Provider (ISP) that hosts SMTP and POP3 servers on behalf of you and all of its other customers. You then point your e-mail software at those servers, and can send and receive messages without having to run your own message store.
Because ISPs are the most commonly known way of getting onto the Internet, many companies start with that approach and keep it as they grow. It's particularly good in companies where many employees work from home or on the road, since they're as likely to be away from the office as in it. With a dial-up ISP account, such workers can use the ISP's local dial-in numbers to get their e-mail wherever they happen to be.
While it's convenient, however, you don't get much control over your messages when they're delivered by an ISP. Because each user downloads his own messages straight from the ISP onto his own computer, there's no way for you to know what's going into or out of the company. There's also no way to create a backup of all the messages you've received, unless you've got a very nice ISP who's willing to set that up for an extra cost.
Because they have to share storage space, ISPs can also be restrictive, limiting the size of incoming e-mails or discarding messages if you receive too many and fill up your inbox. And if you leave the ISP, you may find them less than eager to help you take your e-mail addresses with you.
Doing it in-house
Depending on an ISP's mail becomes problematic as your business grows. This is not because it won't work, but because larger businesses tend to want to get better control of their e-mail. For example, you might want to install a gateway like Clearswift's MAILsweeper, which automatically scans files for viruses and searches outgoing messages for company secrets. Some outsourcers offer virus scanning as an option, but if you want to manage what's caught and what happens to your messages, you'll find you get more control doing it on your own systems.
If you want to bring your mail in-house, you'll need to run your own messaging server. In its easiest form, that means providing your own standard server and investing in a software solution such as Sendmail, Microsoft Exchange, Lotus Domino, or many others.
Additionally, if you invest in your own dedicated messaging server, you are going to need a permanent Internet connection. So if you've been holding off on investing in something like ADSL or ISDN, it's a good idea to look into it; your ISP can no doubt provide some options. Bear in mind though, if you opt for having your messaging needs serviced by an ISP, you do not necessarily need a permanent Internet link.
What do you get for putting in your own messaging server? Mailbox and maximum message sizes limited only by your own hard drive capacity. The ability to build and maintain audit logs of messages, something that's becoming crucial as legal discovery increasingly targets e-mail records. You can install and configure virus and spam filters to your own requirements. And, most importantly, you'll have a good platform to support growth of your business into the online world. While it may cost a few thousand dollars upfront for equipment and software, your investment could pay off in the long term as you expand.
Another model for messaging server hosting is to outsource the entire hosting and operation of your server to a third party. This can either be through a managed service - where you pay a monthly fee per mailbox - or as a fully managed installation of a platform like Microsoft Exchange.
In the former model, the hosting company provides the interface for you to retrieve your e-mail - usually via either POP3 or through a standard Web interface that lets users check their mail from anywhere. Full hosting of messaging is more complex, but may be desirable for companies that plan to build on their messaging server's capabilities. Hosting companies like WebCentral and HostWorks can run Exchange, Notes, and other mail platforms on your behalf.
That means you have zero administration burden, your users can access their mail from anywhere, and you can still access extra features such as virus scanning, the ability to send SMS messages from your systems, and so on. All the integration happens on the service provider's end. If you have special needs, want to impose backup or message archiving policies, well – in the managed services model, money talks.