Email Firewalls

Email firewalls inspect inbound mail before it reaches a recipient. They can delay mail, rewrite links, prefetch images, click links for scanning, or reject content.

Symptoms​

• High delay rates for one recipient domain.
• Opens immediately after delivery.
• Clicks from security-scanner user agents.
• Rejections mentioning policy, content, malware, or reputation.

Response​

Check authentication first, then inspect content, links, attachments, and recipient-domain patterns. If the issue affects one corporate domain, ask the receiving admin to review their gateway logs.