Frequently Asked Questions

What is email deliverability?

Why do emails go to spam?

How do spam filters work?

What affects inbox placement?

What is an email testing tool?

How often should you test emails before sending?

What is transactional vs marketing email?

What is email warm-up and why is it important?

How do I test an email before sending?

What is a seed email test?

What happens when you send a test email?

Can test emails affect sender reputation?

Why does a test email land in spam?

What is an SMTP server?

How do you test an SMTP server?

Why does SMTP connection fail?

What does an SMTP banner tell you?

How do SMTP timeouts affect delivery?

What SMTP ports are used for email sending?

What is STARTTLS in SMTP?

What is HTML in an email?

How can I extract HTML from an email?

Why does email HTML look different in browsers?

Can email HTML affect spam filtering?

What email clients modify HTML?

What is the plain-text version of an email?

Why is plain-text email important?

How do I extract plain text from an email?

What happens if an email has no text part?

How are email attachments encoded?

Why do email attachments get blocked?

How do I extract attachments from an email file?

What attachment types are unsafe in email?

What are email headers?

How do I extract full email headers?

Why are email headers important for troubleshooting?

What is the Received header in email?

How do you analyze email headers?

How can headers reveal email delays?

How do headers show SPF and DKIM results?

What does Authentication-Results mean?

How can I extract links from an email?

Why do email links get flagged as malicious?

What is link tracking in emails?

How do redirects in email links work?

What is SpamAssassin?

How does SpamAssassin score emails?

What is a good SpamAssassin score?

Why does SpamAssassin mark my email as spam?

Can SpamAssassin false-positive legitimate emails?

What is email authentication?

What is SPF and how does it work?

What is DKIM and how does it work?

What is DMARC and why is it important?

What is SPF, DKIM, and DMARC alignment?

What happens if email authentication fails?

What are spam trigger words?

Do spam words still matter in 2025?

How do spam words affect deliverability?

How can I reduce spam words in email content?

Why does invalid HTML break email rendering?

What HTML tags are not supported in emails?

How do you validate HTML code?

Why do email clients strip HTML?

Why does email HTML render differently in clients?

What is email client compatibility?

How do you test email rendering issues?

What causes broken layouts in email HTML?

What is email source code?

How do you analyze raw email source?

What is MIME in email?

How are multipart emails structured?

What is DNS?

How does DNS lookup work?

What is an AAAA record?

What is a TXT record?

What is an SOA record?

What is an MX record?

What is an NS record?

What is a CNAME record?

What is an SRV record?

What is DNSSEC?

What is a DNSKEY record?

What is a DS record?

What is an RRSIG record?

What is NSEC3PARAM?

Why does DNSSEC validation fail?

What is an SPF record?

What does SPF PermError mean?

What is a DKIM selector?

How does DMARC policy work?

What is BIMI?

What is MTA-STS?

Why is email DNS misconfiguration dangerous?

What is ping?

What is traceroute?

Why does traceroute fail?

What is TCP connectivity testing?

What is TLS?

How does HTTPS differ from HTTP?

What is a TLS certificate?

How does TLS handshake work?

What is a certificate chain?

Why do TLS certificates expire?

What causes TLS handshake failures?

What is an IP address?

What is IPv4 vs IPv6?

What is reverse DNS?

What is ARIN?

What is an ASN?

How does IP geolocation work?

Why does IP location show wrong country?

What is my public IP address?

Can my IP address change?

What is a private IP address?

How does a VPN affect my IP?

What is domain health?

How do you check domain reputation?

What causes a domain to be blacklisted?

How long does domain reputation recovery take?