/CONTENT[=offset-specifier]
       /ENV_FROM[=offset-specifier]
       /SUBJECT[=offset-specifier]

    The /CONTENT, /ENV_FROM, and /SUBJECT qualifiers are used to
    specify which frequently occurring fields should be displayed. By
    default, only Subject: fields are shown (/SUBJECT). Use /ENV_FROM
    to display frequent envelope From: fields or /CONTENT to display
    frequent message contents. Any combination of /CONTENT, /ENV_
    FROM, and /SUBJECT may be specified. However, only one of each
    may be used.

    The /CONTENT, /ENV_FROM, and /SUBJECT qualifiers accept the
    optional qualifiers START=n and LENGTH=n. These qualifiers
    indicate the starting offset and number of bytes in the field
    to consider. The defaults are /CONTENT=(START=1,LENGTH=256),
    /ENV_FROM=(START=1,LENGTH=2147483647), and
    /SUBJECT=(START=1,LENGTH=2147483647). Use of these qualifiers
    is useful when, for example, trying to identify occurrences of a
    spam message which uses random text at the start of the Subject:
    line.