SpamfilterN null optin MTA options

Spamfilter MTA options:    (string)
Normally, the simple presence of a spam filter opt-in attribute (the attribute named by the    MTA option or  the attribute named by the    MTA option in a user entry, or the attribute named by the    MTA option in a domain entry) turns on filtering; all the value determines is what sort of filtering will be done. This isn&#x27;t compatible with some directory maintenance and provisioning tools that cannot easily delete an attribute, that always provide the attribute but assume some sort of "off" or "null" value for the attribute is available that doesn&#x27;t enable filtering. The     MTA options allow for better interaction with such directory tools. A     MTA option specifies what value a spam filter optin attribute must have to be ignored (by spam/virus filter package N). The default value for these options is the empty string, which means that by default a present but empty opt-in attribute is ignored.

See also:
 * ldap_optin1 MTA Option
 * ldap_optout1 MTA Option
 * ldap_source_optin1 MTA Option
 * ldap_domain_attr_optin1 MTA Option
 * Spamfilter MTA options