If the SMTP service is set up to route connections, it will use its assigned user map to decide where an incoming connection must be forwarded. This action will only be taken for entries found in the user map. If the destination is not present in the mapping system and no result is returned, then the service will relay the message and normal SMTP policy rules will apply.
NOTE: Because the SMTP service can only be reached from the outside while using the standard port 25, the proxy service should run on this port. Using another port for the proxy setup can render the cluster useless.
NOTE: It is very important to consider the SMTP configuration for the cluster as any changes made for one front-end must be replicated on all of the other front-end nodes. This includes changes in the SMTP Policy script file and the main AXIGEN configuration file.
WARNING: An open relay among the front-end nodes is very hard to spot and can cause many problems with spam and black lists. Special care is recommended while setting up SMTP proxies to prevent such issues.
The SMTP proxy uses the same authentication method as all of the other services that run on that particular node. This is why, in the event that LDAP authentication is used, the same connector will be used for all services.