What do PTR and reverse DNS checks evaluate in email filtering?

PTR (Pointer Record) and reverse DNS (Domain Name System) checks are used to evaluate the origin domain of the sender in email filtering processes. When an email is received, the filtering system can perform a reverse DNS lookup to determine the domain associated with the sender's IP address. This verification helps ensure that the sending server is legitimately associated with the domain it claims to be sending from.

If the PTR record (which maps an IP address to a domain name) matches the domain found in the email's "From" address, it indicates that the sender is likely valid and trustworthy. This check is a critical part of identifying and preventing email spoofing or phishing attempts, where a malicious sender may attempt to disguise their identity by using a forged domain.

The focus on the origin domain enhances the overall security of email communication by helping to authenticate the sender and reduce the risk of spam and malicious emails.