AXIGEN Mail Server can use different Listeners for its TCP services (SMTP Receiving, POP3, IMAP, WebMail, WebAdmin, CLI and FTP Backup) and UDP services (Log and Reporting).

Listeners are network points of entry, associated with an interface address and port number that grant access to a specific TCP or UDP service.

Listeners add extra flexibility and configurability to each AXIGEN service, as they can be used to grant differentiated access to the same services for different categories of users (e.g users within a specific domain). Moreover, listeners can be associated with a variety of rules that allow defining specific limitations for connections coming from IPs within specified IP sets.

Listeners can be defined, using various parameters corresponding to that TCP service, from the configuration file (as of type "TcpListener" OBJECT-SET) or through WebAdmin (the web configuration interface). UDP service listeners have fewer parameters associated as connection related parameters do not apply to them.

The following attributes are available for each listener:

address - the "point of entry" address and port number

enable - specifies whether the listener is enabled or not (this way you won't have to delete the listener when you want to discontinue its use)

max. number of simultaneous connections and max. number of new connections in a defined time interval (seconds/minutes/hours/days) - parameters specifying limitations for network connections accepted for this listener

max. connections from each remote IP address and max. connections from each remote IP address in a defined time interval (seconds/minutes/hours/days) - parameters specifying limitations for network connections from the same IP address accepted for this listener

TCP listeners can also be set to support SSL connections. Further SSL parameters are available for TCP listeners in AXIGEN:

allowed SSL versions

certificate file

Max. chain verification depth

Use Ephemeral Key

Request certificate-based authentication from client

and others.

Below you can find a scheme for a quick understanding of the Log listeners: (in this context ':' can be translated as 'of type'):

TCP service:

'listeners' : 'TcpListener' OBJECT-SET
'allowRules' : 'TcpAllowRule' OBJECT-SET
'denyRules' : 'IpRule' OBJECT-SET

UDP service:

'listeners' : 'IpListener' OBJECT-SET

For more information about the usage of these parameters in WebAdmin and specific details on their values and how to set them see Adding and Editing TCP Listeners. You can also configure listeners using the CLI tool, for more information see Configuring AXIGEN using CLI.