legitimate invoice macro attachment quarantined; filter rule failed the ap workflow

TL;DR

Macros in invoices are a real business pattern in some supply chains and a classic malware carrier everywhere else, so the filter is doing its job bluntly. The fix is not to allow macros generally: verify this sender and format, confirm the files are clean by detonation and vendor contact, then scope delivery to that sender and AP recipients, ideally while pushing the vendor toward a macro-free format or a portal.

legitimate invoice macro attachment quarantined; filter rule failed the ap workflow

Use this when

• AP cannot process invoices because macro files from a known vendor are quarantined.
• Only one vendor flow is affected while other mail works.

Not for this skill when

• The macro attachment is from an unknown or first-time sender. Keep it quarantined and verify out of band first.
• Detonation found actual malicious behaviour. It stays blocked; escalate with the vendor as a possible compromise.

Steps

1. Identify the held messages: sender, file type and the exact policy that quarantined them. Verify: the blocking policy and sample set are named.
2. Verify the vendor and the invoice expectation through the AP contact record, and detonate one sample fully to confirm clean behaviour. Verify: sender legitimacy and file cleanliness are both evidenced.
3. Release the held invoices to AP and note them in the case so the pattern is auditable. Verify: AP confirms receipt and processing resumes.
4. Create a scoped exception for that authenticated sender to the AP group, with the macro file type named and an expiry for review. Verify: the exception cannot apply to other senders.
5. Ask the vendor to move to PDF invoices or a portal, and set the exception to lapse when they do. Verify: the vendor request is sent and the review date is set.

Variant phrasings

invoice macro attachment quarantined legitimate vendor exception

The scoped exception variant.

safe attachments blocks macro invoices accounts payable

The AP workflow variant.

Compatibility: Defender Safe Attachments policies and scoped sender exceptions in gateway products.

Why it happens

The collision is structural: macro documents are simultaneously a legacy accounting format and the oldest malware delivery trick in mail. Filters resolve it by defaulting to block, pushing the nuance onto tenant exceptions, which is correct behaviour that needs active management.

Edge cases / pitfalls

• Authenticate the sender requirement matters: an exception keyed only on a spoofable address is an open door. Require SPF and DKIM pass in the exception conditions where possible.
• Review macro exceptions quarterly; vendors do migrate formats and forget to tell you.
• AP teams under payment pressure are the release valve attackers count on. Keep the verification step with IT, not AP.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_vbBXk5Nd519DjXO8SV5duA