OpenDKIM

OpenDKIM is an open-source software tool that implements DKIM (DomainKeys Identified Mail) for email systems. Essentially, it helps verify the authenticity of emails and prevents email spoofing. Here’s a breakdown:

Purpose

• DKIM adds a digital signature to the headers of outgoing emails.
• The signature allows receiving mail servers to verify that:
  1. The email was actually sent by the domain it claims to be from.
  2. The message was not altered during transit.

OpenDKIM handles creating and verifying these signatures.

How It Works

1.) Signing outgoing mail:

• OpenDKIM uses a private key associated with your domain.
• It signs specific headers of outgoing emails (like From, Subject).
• The signature is included in the email as a DKIM-Signature header.

2.) Verifying incoming mail:

• When an email arrives, OpenDKIM can check the signature using the public key published in the sending domain’s DNS records.
• If the signature matches, the email is considered authentic.

Components

• Milter interface: Integrates with mail servers like Postfix or Sendmail.
• Key management: Handles generating and storing DKIM keys.
• Policy enforcement: Can reject emails failing DKIM verification.

Benefits

• Protects your domain from being used in phishing or spam.
• Improves email deliverability because mail providers trust DKIM-signed emails.
• Works with SPF and DMARC for comprehensive email authentication.

In short, OpenDKIM is a tool that signs and verifies emails to make sure they’re truly from your domain and haven’t been tampered with.