The Axigen messaging solution includes a Domain Name Resolver (DNR) module used to extract information from domain servers. The module implements the specifications from RFC1034 and RFC1035 and communicates with Domain Name Servers using UDP sockets on port 53.
Axigen services using DNR:
- The SMTP Receiving service uses DNR for performing the SPF tests (this action involves PTR and TXT queries).
- The SMTP Sending service queries DNR for MX and A information about the domain where to relay the mail messages.
All Axigen main services can log different types of events. You can specify what events are logged, where and how they are logged.
In this section you can configure the time period after the first DNR query is closed, maximum number of DNR query retries to be executed and number of results (IP addresses) cached for each DNR query type to be executed.
When performing DNR searches, Axigen uses a list of known nameservers (specified in the OS configuration). In order to limit bandwidth and time consumed with DNS traffic, a list of known hosts can be defined. Different priority values can be assigned to nameserver IPs to set the order in which you wish to query nameservers (the servers with the higher priority are queried first).