Is the LDAP service mandatory for analyzing whether an incoming traffic is a form of DHA attack?

Technically, LDAP service is not required. The DHA rule of IMSS 7.1 relies on the result returned from Postfix, which in turn passes the result to FoxProxy, a sub-module of IP Profiler, for analysis. The LDAP server is just one of the many means by which Postfix checks for the existence of a recipient’s mailbox.

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Is the LDAP service mandatory for analyzing whether an incoming traffic is a form of DHA attack?