Question 1

What is email authentication?

Accepted Answer

Email authentication verifies sender identity using SPF, DKIM, and DMARC protocols. SPF lists authorized mail servers, DKIM adds cryptographic signatures, DMARC defines policy for failures. Prevents spoofing, phishing, domain impersonation. Improves deliverability - unauthenticated emails often marked spam. Required by Google/Yahoo (2024) for bulk senders. Authenticate your domain to protect brand reputation and ensure inbox delivery.

Question 2

What is SPF and how does it work?

Accepted Answer

Sender Policy Framework (SPF) is DNS TXT record listing authorized mail servers for your domain. Example: v=spf1 ip4:192.0.2.0 include:_spf.google.com ~all. Recipient checks: sending server IP matches SPF record? Pass = authenticated, fail = potential spoof. Mechanisms: ip4, ip6, include, a, mx. Qualifiers: + (pass), - (fail), ~ (softfail), ? (neutral). Limit: 10 DNS lookups maximum.

Question 3

What is DKIM and why is it important?

Accepted Answer

DomainKeys Identified Mail (DKIM) adds cryptographic signature to email headers. Private key signs email, public key in DNS validates signature. Proves: email from authorized server, content unmodified in transit. Example DNS record: selector._domainkey.example.com TXT "v=DKIM1; k=rsa; p=MIGfMA0GCS...". Survives forwarding. Required with SPF/DMARC. Multiple selectors supported (rotate keys). Signature header: DKIM-Signature: v=1; a=rsa-sha256...

Question 4

What is DMARC and how to configure it?

Accepted Answer

Domain-based Message Authentication, Reporting and Conformance (DMARC) builds on SPF/DKIM. Defines policy for authentication failures: none (monitor), quarantine (spam folder), reject (block). Example DNS record: _dmarc.example.com TXT "v=DMARC1; p=quarantine; rua=mailto:reports@example.com". Provides aggregate reports (rua) and forensic reports (ruf). Start with p=none, monitor reports, gradually enforce to p=reject.

Question 5

Why do emails fail authentication?

Accepted Answer

Common failures: SPF - sending from unauthorized server, too many DNS lookups, missing include. DKIM - invalid signature, key rotation without DNS update, email modified in transit. DMARC - SPF/DKIM alignment failure, no policy defined. Forwarding breaks SPF (but DKIM survives). Check: DNS records correct, selectors match, domains aligned (envelope vs header). Use email authentication validators to diagnose issues.

Question 6

How to prevent email spoofing?

Accepted Answer

Implement all three: SPF (authorize servers), DKIM (sign emails), DMARC (enforce policy). Set DMARC policy p=reject for maximum protection. Enable DMARC reports to monitor. Add BIMI (Brand Indicators for Message Identification) for logo display. Monitor: spoofed domains using your brand, authentication failures. Train employees: verify sender, check for phishing. Use email security gateway. Report spoofing to authorities (FBI IC3).

Question 7

What is DMARC alignment?

Accepted Answer

DMARC requires identifier alignment - domain in From: header matches authenticated domain. SPF alignment: From header domain aligns with Return-Path domain (relaxed or strict mode). DKIM alignment: From header domain aligns with d= domain in DKIM signature. Example: email from @example.com must pass SPF/DKIM with @example.com domain. Alignment prevents display name spoofing. Check alignment in DMARC reports.

Question 8

How to improve email deliverability?

Accepted Answer

Authentication is foundation. Configure: SPF (authorize servers), DKIM (sign with 2048-bit key), DMARC (p=quarantine/reject). Best practices: warm up new IPs, maintain clean email list, low bounce/complaint rates, authenticate subdomains, enable BIMI, monitor blacklists, use dedicated IP for bulk sending, avoid spam trigger words, provide unsubscribe, follow CAN-SPAM/GDPR. Monitor inbox placement with seed lists.

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