SPF MTA options

A number of MTA options exist affecting SPF lookups. Note that SPF lookups are enabled via channel options such as ; the MTA options affect the interpretation of SPF results and errors. See also the  mapping table,  which may be used to avoid performing actual DNS lookups for selected (typically local) domains. See also the SRS MTA options, as many sites using SPF will also want to enable SRS address encoding.

Sender Policy Framework, or SPF, formerly referred to as Sender Permitted From, is a mechanism that attempts to prevent email forgery. It works by looking up special TXT records associated with the domain in the MAIL FROM (envelope from) address. This operation (which can actually involve several DNS lookups) eventually produces a list of IP addresses that are authorized to send mail from the domain. The IP address of the SMTP client is checked against this list and if it isn&#x27;t found the message may be considered to be fraudulent. MTA support for SPF was implemented in MS 6.3-0.15.

See also the  MTA options which configure the error text issued in cases of SPF errors.

See also:
 * spf_smtp_status_fail MTA Option
 * spf_smtp_status_fail_all MTA Option
 * spf_smtp_status_permerror MTA Option
 * spf_smtp_status_softfail MTA Option
 * spf_smtp_status_softfail_all MTA Option
 * spf_smtp_status_temperror MTA Option
 * spf_max_dns_queries MTA Option
 * spf_max_recursion MTA Option
 * spf_max_time MTA Option
 * error_text_spf_temperror_4 MTA Option
 * error_text_spf_temperror_5 MTA Option
 * error_text_spf_permerror_4 MTA Option
 * error_text_spf_permerror_5 MTA Option
 * error_text_spf_fail_4 MTA Option
 * error_text_spf_fail_5 MTA Option
 * error_text_spf_softfail_4 MTA Option
 * error_text_spf_softfail_5 MTA Option
 * spfhelo Option
 * SPF_LOCAL mapping table
 * SRS MTA options
 * MTA options