The term Mail Hub is used to denote an MTA (message transfer agent) 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 (mail user agent) access. Examples could include dedicated anti-SPAM appliances, anti-virus engines running on dedicated hardware, email gateways and so forth.

DNS Based Mail Hub

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 An Internet service provider (ISP) is an organization that provides a myriad of services related to accessing, using, managing, or participating in the Internet. ISPs can be organized in various forms, such as commercial, community-owned, no ...

(ISP), or for a

FOSS Free and open-source software (FOSS) is software available under a license that grants users the right to use, modify, and distribute the software modified or not to everyone free of charge. FOSS is an inclusive umbrella term encompassing free ...

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. Simple

DNS The Domain Name System (DNS) is a hierarchical and distributed name service that provides a naming system for computers, services, and other resources on the Internet or other Internet Protocol (IP) networks. It associates various informatio ...

MX record based Mail Hub cluster with parallelism and front-end failover and load balancing is illustrated in the following diagram: The servers would be all

Linux Linux ( ) is a family of open source Unix-like operating systems based on the Linux kernel, an kernel (operating system), operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically package manager, pac ...

x86 x86 (also known as 80x86 or the 8086 family) is a family of complex instruction set computer (CISC) instruction set architectures initially developed by Intel, based on the 8086 microprocessor and its 8-bit-external-bus variant, the 8088. Th ...

servers with low cost

SATA SATA (Serial AT Attachment) is a computer bus interface that connects host bus adapters to mass storage devices such as hard disk drives, optical drives, and solid-state drives. Serial ATA succeeded the earlier Parallel ATA (PATA) standard ...

or PATA hard disk storage. The front-end servers would most likely run Postfix with

Spamassassin Apache SpamAssassin is a computer program used for e-mail spam filtering. It uses a variety of spam-detection techniques, including DNS and fuzzy checksum techniques, Bayesian filtering, external programs, blacklists and online databases. It ...

and

ClamAV ClamAV (Clam AntiVirus) is a free software, cross-platform antimalware toolkit able to detect many types of malware, including viruses. It was developed for Unix and has third party versions available for AIX, BSD, HP-UX, Linux, macOS, OpenVMS, ...

. This

RAIS (), plural , is an Arabic title meaning 'chief' or 'leader'. It comes from the word for head, . The corresponding word for leadership or chieftaincy is . It is often translated as 'president' in Arabic, and as 'boss' in Persian. Swahili speak ...

server

Cluster may refer to: Science and technology Astronomy * Cluster (spacecraft), constellation of four European Space Agency spacecraft * Cluster II (spacecraft), a European Space Agency mission to study the magnetosphere * Asteroid cluster, a small ...

would then overcome the problem with

Perl Perl is a high-level, general-purpose, interpreted, dynamic programming language. Though Perl is not officially an acronym, there are various backronyms in use, including "Practical Extraction and Reporting Language". Perl was developed ...

based

being too CPU and memory hungry for low cost servers. The solution presented here is based on all

GPL The GNU General Public Licenses (GNU GPL or simply GPL) are a series of widely used free software licenses, or ''copyleft'' licenses, that guarantee end users the freedom to run, study, share, or modify the software. The GPL was the first c ...

free software, but of course there are alternative configurations using other free or non-free software.

References

Mail Clustering

ISOC, 2005. Email {{comp-stub