Service Update
| Availability | November 18th, 2025 |
| Product(s) | Email Security Cloud Gateway (CG) |
| Who's affected | Email Security Cloud Gateway, Administrators |
Overview
Mimecast is pleased to announce enhancements to the Event Push integration, enabling organizations to automatically send security and operational events from Mimecast to external platforms in a variety of formats. This integration supports use cases such as pushing logs to SIEM, triggering SOAR workflows, and storing events in AWS S3 for long-term retention analytics.
What's changing
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Multiple Event Push Types Supported:
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HTTP Event Collector (HEC): Batch JSON payloads for high-volume SIEM ingestion (e.g., Splunk, CrowdStrike).
NDJSON: Newline-delimited JSON for efficient bulk event delivery.
Webhook: Single-event JSON payloads for real-time automation (note: not recommended for high-volume event types due to rate limiting).
AWS S3 File: Uploads each event as a JSON file to a specified S3 bucket (note: subject to AWS PUT rate limits).
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Expanded Event Types:
- Now includes Attachment Protection, Impersonation Protection, URL Protection, DLP/Content Examination, Audit, Message Release, Archive View, Message Rejection, Email Queue Status, MTA, Threat, Remediation Incident, and Threat Feed events.
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Flexible Authentication:
- OAuth 2.0, static headers (with secret masking), and IP-based authentication options.
- AWS S3 authentication via IAM Access/Secret Key and region.
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Enhanced Security and Compliance:
- All events must be sent over HTTPS (port 443) to endpoints with publicly valid certificates.
- Ability to restrict API traffic to specific Mimecast IP addresses.
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Improved Error Handling:
- Automatic retries for temporary errors.
- Email notifications for permanent errors to up to 5 configured recipients.
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Replay and Fetch Controls:
- Fetch from Duration setting to control historical event delivery on setup.
- Token reset feature for replaying events as needed.
Recommended actions
- Review your current Event Push configurations to ensure the selected push type matches your event volume and recipient platform's capabilities.
- Update recipient platforms to accept connections from the listed Mimecast IP addresses.
- Verify authentication settings (OAuth 2.0, static headers, or IAM credentials) and update secrets as needed.
- Monitor for rate limiting if using Webhook or S3 push types with high event volumes; consider switching to HEC or NDJSON if necessary.
- No immediate action is required if your current configuration meets your needs and is functioning as expected.
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