From now on, Mailtrap sends all webhook callbacks from a fixed set of Mailtrap-owned IPv4 CIDR blocks: 45.158.83.0/24 and 5.181.200.0/24. The same IP ranges also cover SMTP sending.

This gives you predictable, stable IPs that replace dynamic AWS addresses, a tighter security posture by whitelisting just two /24 blocks instead of the entire AWS IP pool, and consistent test & production behavior since webhook test calls use the same IPs as real traffic. 

Static IPs are especially useful if:

• Your endpoint is behind a corporate or on-premise firewall.

• You're in a regulated industry (finance, healthcare, insurance) with strict network policies.

• Your security team requires an explicit allowlist for all inbound traffic.

• You're automating infrastructure and need static CIDRs for IaC/Terraform templates, including SOC-2 compliant environments that block unknown IPs.

For more information, please read the in-depth Knowledge Base article.