How do attachments affect spam filtering?

Attachments significantly increase the complexity of spam filtering because they can carry malware, phishing documents, and other threats. Filters apply additional scrutiny to messages with attachments.

Certain file types are blocked outright by many systems. Executables (.exe, .bat, .cmd), scripts (.js, .vbs), and some archive formats (.zip with executables inside) are commonly blocked regardless of content.

Microsoft Office files with macros receive extra scrutiny because macro malware is prevalent. Some filters disable macros or sandbox documents before delivery.

PDF files are generally safer but still scanned for embedded links and scripts. Large attachments may be rejected for size limits rather than spam concerns.

For deliverability, consider hosting files and linking to them rather than attaching. This avoids attachment filtering and provides better tracking.

Attached cargo requires thorough inspection. Sometimes a link to your warehouse is safer than bringing the goods aboard.