An email hosting service is an Internet hosting service that runs email servers.
Email hosting services usually offer premium email at a cost as opposed to advertising supported free email or free webmail. Email hosting services thus differ from typical end-user email providers such as webmail sites. Email hosting cater mostly to demanding email users and Small and Mid Size (SME) businesses, while larger enterprises usually run their own email hosting service. Email hosting providers allow for premium email services along with custom configurations and large number of accounts. In addition, hosting providers manage user's own domain name, including any email authentication scheme that the domain owner wishes to enforce in order to convey the meaning that using a specific domain name identifies and qualifies email senders.
Most email hosting providers offer advanced premium email solutions hosted on dedicated custom email platforms. The technology and offerings of different email hosting providers can therefore vary with different needs. Email offered by most webhosting companies is usually more basic standardized POP3 based email and webmail based on open source webmail applications like Horde or Squirrelmail. Almost all webhosting providers offer standard basic email while not all email hosting providers offer webhosting.
The term Mail Hub is used to denote an MTA or system of MTAs used to route email but not act as a mail server (having no end-user email store) since there is no MUA access. Examples could include dedicated anti-SPAM appliances, anti-virus engines running on dedicated hardware, email gateways and so forth.
A first example for a Mail Hub consisting of a network of MTAs would be that of a typical small-to-medium size Internet service provider (ISP), or for a FOSS corporate mail system. This solution is very good for developing nation ISPs and NGOs. As well as any other low-budget but high availability mail system needs. This is mostly due to not using expensive Network level switches and hardware.
The servers would be all Linux x86 servers with low cost SATA or PATA hard disk storage. The front-end servers would most likely run Postfix with Spamassassin and ClamAV. This RAIS server Cluster would then overcome the problem with Perl based Spamassassin being too CPU and memory hungry for low cost servers. The solution presented here is based on all GPL FOSS free software, but of course there are alternative configurations using other free or non-free software.
