Tag: Email Security

SMTP-AUTH: Securing Email Transmission and Preventing Spam Relay

May 14, 2026

SMTP was designed without any security features — messages are transmitted as unencrypted ASCII and can be easily forged. There is no mechanism for verifying sender identity or message integrity. SMTP-AUTH addresses this by requiring clients to authenticate with the mail server before sending.

SMTP Security Risks Without AUTH

  • Email messages can be read by any party along the routing path.
  • Messages can be forged with a fictitious or stolen “From” address.
  • No message integrity or sender verification guarantees exist.
  • SMTP flooding attacks overwhelm servers by opening massive numbers of simultaneous connections.

SMTP-AUTH Benefits

  • Allows legitimate users to send mail from any IP worldwide — essential for mobile workers.
  • Denies relay service to spammers and unauthorised users.
  • Supports alternate SMTP ports, bypassing ISP blocks on the default port 25.
  • Creates an audit trail for tracing the source of spoofed or abusive email.

E-mail Spoofing: Forged Emails and How to Detect and Prevent Them

May 14, 2026

E-mail Spoofing is the forgery of an email header so that a message appears to originate from someone or somewhere other than the actual source. Since SMTP does not require authentication, a sender can set any “From” address — whether fictitious or stolen.

Why Spoofed Email is Dangerous

  • Tricks users into changing passwords or sending sensitive files (impersonating IT admins).
  • Facilitates social engineering by impersonating people in authority.
  • If your address is used as the return address for spam, your domain may be added to blocklists.

Prevention Guidance

  • Cryptographic Signatures: Use PGP or S/MIME to digitally sign and authenticate email.
  • SMTP Port Lockdown: Prevent direct external SMTP connections to your mail server.
  • SMTP-AUTH: Require authentication for all outbound relay.
  • Centralised Logging: Route all inbound SMTP through a single hub for unified log analysis.
  • User Education: Train users to never disclose passwords via email regardless of sender identity.
  • Domain Name Checks: Verify source domain existence on the recipient server (SPF records).