Alright, let me set the scene for this particular circle of integration hell. We're mid-migration from a legacy on-prem SIEM to ThreatConnect, and of course, the promised "low-code" email ingestion pipeline is the first thing to crumble like a sandcastle at high tide. The specific pain point? Our secure mail gateway (a Proofpoint variant) is apparently too *secure* for TC's parser to handle.
The issue isn't that emails don't arrive; they do. The issue is that the parser, which works fine with a vanilla Office 365 feed, chokes on the MIME structure and headers the gateway stamps on everything. We're left with empty incident fields, missing attachments, and a log full of cryptic parser errors that are about as helpful as a screen door on a submarine.
Here's the gist of our setup and where it's failing:
* **Ingestion Source:** We're using the dedicated ThreatConnect email address, routing through our `securemail.company.com` gateway.
* **Parser Configuration:** We've tried both the default "Email" parser and a custom one we built to be more forgiving.
* **The Smoking Gun:** When we bypass the gateway and send a test from a personal Gmail account, the parser works perfectly. This confirms the gateway's wrapper is the culprit.
The most telling error pattern in the parser log looks something like this:
```
ERROR [EmailParserThread-3] ... Failed to locate main content body.
ERROR [EmailParserThread-3] ... Header 'Message-ID' not found in MIME parts.
WARN [EmailParserThread-3] ... Attachment filename extraction failed, defaulting to 'unnamed.dat'.
```
Our current working theory is that the gateway is either:
1. Nesting the original email as a `message/rfc822` attachment, effectively burying the data the parser needs.
2. Rewriting critical headers (`Message-ID`, `From`, `Subject`) in a way that breaks the parser's expected traversal of the MIME tree.
We've tried the obvious:
* Adjusting parser settings for "Allow nested messages" and "Ignore parsing errors" (which just creates empty incidents).
* Adding custom header-mapping rules in the parser definition, which feels like trying to perform surgery with oven mitts on.
**The real question for the community:** Has anyone successfully navigated this specific minefield with a secure gateway (Proofpoint, Mimecast, IronPort, etc.) and ThreatConnect's email parser? Did you:
* Create a pre-processing script to "defang" the gateway's MIME envelope before it hits TC?
* Find a magical combination of parser settings we've missed?
* Give up and use a different ingestion method (like writing to an S3 bucket and using a different poller)?
I'm knee-deep in MIME docs and RFCs, which is not where I wanted to spend this quarter. Any war stories or proven config snippets would be a lifeline.
-warrior
Expect the unexpected