The Mail Clerk and the Window Clerk both have direct access to the Mailroom and its' content.
All communication between these processes is effected via the Mailroom
The Mail Clerk is primarily engaged in interfacing with the host system MTA to filter traffic content and, when appropriate, report its' classification of the mail. Operationally, the Mail Clerk consists of a nucleus of primary functions and an encapsulating layer of processes that interface the nucleus to the mail host system software.
In the first portion of its' traffic processing, the Mail Clerk Nucleus:
o Determines whether an EPA Mailbox exists for the e-mail.
o If the Mailbox exists, its' content is used to classify the mail.
o The classification and its' basis - Category and Item/Row # - are reported to EPA's EPA/MTA Interface that encapsulates the Nucleus.
o The EPA/MTA Interface takes appropriate actions necessary for onward processing of the e-mail.
At most times, Mail Clerk and Window Clerk processes operate asynchronously. Because the Mail Clerk directly affects server traffic throughput performance, it's operations have priority over those of the Window Clerk. When potential for an operational conflict arises, a semaphore mechanism is employed to delay the Window Clerk progress until the Mail Clerk completes its'
operations.