MX Nodes – clusters of MX Servers

All inbound email is handled by multiple MX Servers clustered together to form what we call MX Nodes. Each node is able to process hundreds of thousands of emails per hour without introducing delays. Additional servers can be added to a Node within minutes to increase capacity should the need arise.

The MX Nodes store their configuration information in an LDAP database, whilst log files and various elements of the spam scanning system are stored in a relational database. LDAP and the database are set-up to replicate in real time which means that should an administrator make changes to domain settings, these changes are picked up almost instantly by all MX Nodes. The use of a replicated architecture means that MX Nodes can be placed at various strategic geographic locations for increased performance and redundancy and allows the system to scale very quickly. Currently, two MX nodes are located in the primary data centre, whilst a third is located in the USA with other Nodes planned for other UK and European locations during the first half of 2009.

MX Nodes perform recipient address verification against the destination servers to protect against directory harvesting attacks.

Email domains can be configured with a range of delivery options including: multiple primary & secondary destination servers, archiving to single target mailbox, spam rejection/identification settings, white/black lists and file type blocking.

If email domains are configured with Virus and/or Spam Protection Services on their account, the MX Nodes are responsible for handing the email over to the Spam & Virus Scanning System where it is subjected to a comprehensive range of checks by multiple different scanning engines and techniques to ensure the email is OK before processing it further.

If email domains are configured with Continuity Email Services on their account, the MX Nodes also handle Continuity Email routing such as cloning a copy of incoming emails to the Zimbra Continuity Mailboxes, forwarding original emails to the destination servers and dealing with queueing of emails during a continuity incident and subsequent repatriation of sent items once the client server(s) comes back on-line.

Once an email has been accepted, the MX Nodes will forward the emails on to their intended destination servers - either at the customer site or to the Zimbra Mailboxes servers.