How to configure your server for maximum inbox delivery
As mentioned before proper server configuration can keep you off black lists, but proper configuration can also allow recipient ISPs to validate that your e-mail headers were not forged.
For example, Sender Policy Framework (SPF) records are Domain Name System (DNS) records that prohibit e-mail spammers from forging the ‘From’ fields in e-mails. These records state on the DNS level which servers are allowed to distribute e-mail for a domains behalf. SPF records are looked at by incoming mail servers and they then check the IP in the headers against the SPF records in the DNS. A match may or may not help you get into the inbox. However, if somebody attempts to forge e-mail claiming to be from you and the SPF records do not match, then those e-mails will likely land in the junk. In short, SPF records can be used to help prevent your name from being tarnished.
However, since the e-mail headers are sent in plain text, even SPF records could potentially be spoofed. Spoofing is a type of online forgery where by one entity claims to be somebody they are not. In 2007, DomainKeys Identified Mail (DKIM) was released. The purpose of DKIM is to ensure the message in its entirety was kept intact and this can only be done by a properly configured server with a DNS txt record which specifies the proper DomainKey. When an incoming mail server receives an e-mail, they retrieve the public key from the DNS txt record and decrypt the e-mails signature which in turn validates the domain name identity associated with the message. As with SPF records, DKIM may or may not help you land in the inbox. But properly configured DKIM can prevent third parties from using your domain name in a malicious way.