The EPA Mail Clerk must function identically in many hardware and software environments to meet design objectives. To assist licensees
with implementation and integration into mail server software, the EPA Mail Clerk is functionally defined as consisting of two software
modules - an EPA ENVIRONMENTAL INTERFACE (EEI) and an EEI-embedded, host-system-insulated
EPA OPERATIONS NUCLEUS (EON).
Depending on the mail server software environment and the EPA licensee's implementation choices, an e-mail may appear as either a
completely-assembled information structure or as a series of 'snapshots' of the assembly process.
A UNIX/'sendmail' environment mail filter ('milter') presents each field to the EEI upon arrival for assembly and expects a response
which determines subsequent server processing. The EEI has the option to present the EON with each e-mail field upon arrival or to
assemble the entire e-mail before presenting it to the EON. This mode of operation offers some operational efficiency and economies.
Most other mail server software environments do not support such field-by-field interaction or - in fact - ANY interaction.
Hence, the general case of EPA operation will be for the EEI to acquire the entire assembled e-mail and present it to the EON for
filtering and classification. In this context, the EEI constitutes a universal mailbox to which the mail server software will
deliver all assembled e-mails.
Once the EEI has interacted with the EON to determine mail classification, the EEI has the ability to invoke any server-system
process with inputs consisting of the e-mail and its' classification reasons for subsequent disposition of the e-mail.
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