Sender Policy Framework or SPF validates the Vs. domain the SMTP server response, from which the email originates.
This methodology to ensure that the email was actually sent by the server where the sender domain is configured.
The SPF settings are performed and managed by the BIND (Berkeley Internet Name Daemon) or other installed DNS service, which manages the domains and their addresses.
Example of SPF configuration:
v=spf1 a mx o_meu_domain.com ip4:9.110.8.1 ? all
SPF Official Website: http://www.openspf.org/
Domainkeys Identified Mail or DKIM validates whether the content of the email during your transport has not changed, in its content or headers.
Also validates if email attachments, if any, were not changed during transport from sender server to recipient server.
In the case of DKIM, a digital signature is included in all emails sent from the sending server.
This case, in light of computer security, is extremely interesting due to the number of stakeholders used in the verification of the emails sent, since the MTA, Openssl, DNS.
Example of a DKIM:
DKIM-Signature: v=1; a=rsa-sha256; d=o_meu_domain.com; s=Brisbane;
c=relaxed/simple; q=dns/txt; l=1234; t=1117574938; x=1118006938;
h=from:to:
bh=Mtizndu2nzg5mdeymzq1njc4otaxmjm0nty3odkwmti=;
b=dzdVyOfAKCdLXdJOc9G2q8LoXSlEniSbav+yuU4zGeeruD00lszZ
Vog4zhrniyzr
Official website of DKIM: http://www.dkim.org/