Shared Email Hosting means that the same server (computer) hosts more than one domain (i.e with another website). With the powerful processors of today, it's not at all unusual to find hundreds of websites to be hosted on a single server. The best thing about Shared or Virtual hosting is that it allows individuals and businesses with limited financial resources to establish an online presence with almost all the bells and whistles associated with a Dedicated Server.
The price for a Shared Hosting account however, is low compared to the Dedicated Server solution. It can even be in some instances very low! Generally those are the times when you have to be careful.
Shared Hosting is where multiple accounts (domains) are hosted on the same server; each account is contained within its own folder or location on the server to keep it separate from other accounts which are hosted on that server. Shared Hosting is seen as the most affordable Web Hosting since the cost of server maintenance as well as other server related costs are spread across a large amount of customers. Shared Hosting is normally where most webmasters begin, and then work their way up the chain to eventually owning a Dedicated Server; this is because Shared Hosting packages are generally very cheap, and the amount of skilled needed to begin with is very low. Shared Hosting is normally only available on two different types of operating system: Linux and Windows. This is because most web applications are built to suite either one of these platforms, and hosting control panels are only mainly made for Linux and Windows. One thing to note though is that there are a few hosts who do offer Shared Hosting on BSD based systems, although BSD operating systems are only normally available on Dedicated Servers.
Problems that are common in a Shared Hosting environment:
1. Overcrowded servers
This problem is one of the most common in the Web Hosting industry (in the Shared Hosting section of it). In the world of Web Hosting, a crowded server is not a good sign, as it is for gamers. Rather, it suggests that either some clients on the server are resource hogs or that the web host has been overselling its server space and resources. This problem is one that you must investigate when looking at hosting options.
2. Security issues
In a perfect world, all a Web Hosting company would need to do would be to connect the server to the Internet and keep things running smoothly on the server. The Internet is not exactly a peaceful place though. There are all kinds of internet "terrorists". They're sometimes called hackers, sometimes they're called crackers. It doesn't matter what you call them, the important thing is that they're out there and that they make the life of every decent hosting business harder than it should be.
Hackers and crackers are extreme cases; however on the net, regular people behave in a different manner than in real life. When hundreds of people have access to a computer (the server) there are real chances to find that one of them is... less than honest.
In addition, in a Shared Hosting environment it's not that uncommon to find that you can easily access other people's accounts (a Shared Hosting account is basically a directory (folder) on a server's hard disk). Fortunately this is usually not something critical, as in most cases what you store on the server is meant to be visible to the public anyway.
Generally, a server used to host more websites is usually not as secure as a Dedicated Server. There's usually a trade-off between security and freedom, just as in real life.
3. Neighborhood related problems
The - what I call - "neighborhood problems" are complex issues, all having a common trait: they all involve what the other people are doing on that server. Those people (and their websites) are your closest online neighbors and they're just as important as your real-life neighbors are.
If one of those neighbors is using the account to test new scripts (and he's really bad at coding) then you (and everybody on that server) risks that one day, one of those badly written scripts might crash the server. That means at least a couple of minutes of downtime.
There is also another important neighborhood related thing that has to do more with the inner workings of the Internet than with people. Chances are that your site is sharing the IP with a number of other sites. Now, if a spammer happens to find a temporary home on that server, the IP where the spam originates from might be listed in a spam list and this can lead to your emails not being received by servers throughout the web.
However, a dedicated IP doesn't solve the emails problem because while your account will indeed have an IP of its own, the emails will still be relayed through a single, shared IP.
Advantages:
The first advantage is the low price. The second advantage (which most web hosting customers don't even fully realize) is that the client doesn't have to manage the server. Managing a server is a complicated job, done by professionals. Hiring someone for this job is not a feasible thing to do for most website owners.
For most people shared hosting is the pretty much the only feasible choice. That's why most don't even think of or have never heard of other types of hosting.
Conclusions:
No matter what the disadvantages are, it's clear that the Shared Hosting solution is here to stay. The vast majority of websites today use Shared Hosting and the reason is obvious: it s advantages overweigh its disadvantages. Unless your website is so big that it really needs the computing power and the space offered by an entire server, Shared Hosting is most likely to be the right solution for you too.