Technical

What causes SPF verification failures for emails forwarded to Gmail?

Do Apple email filters use Proofpoint or Cloudmark?

What are the deliverability and security implications of embedding versus hosting email signature images?

How do ESPs reliably distinguish human vs. bot email opens and clicks?

Strategies for email address verification and improving deliverability without double opt-in

Why are Microsoft Outlook 550 5.7.515 access denied errors occurring due to DKIM failures, and how do message encoding and modification affect them?

How do Microsoft sender requirements determine email reply capability, and how do CNAMEs affect MX records for reply-capable subdomains?

How to configure email authentication and warm up subdomains for improved deliverability and to avoid anti-phishing warnings?

How can I lookup and categorize MX records for a large list of email addresses?

How do I create an image pixel for tracking email opens and clicks?