Limitations and Precautions for Mail Filtering

Hardware Requirements

The mail filtering function is supported by all models.

The USG6510E/6510E-POE/6530E does not support RBL-based anti-Spam function.

License Requirements

The mail filtering function is not license-controlled.

Component package Requirements

The mail filtering function is dependent on the content security component package. However, it does not require the content security component package be manually loaded. The content security component package is directly placed in the software package and automatically loaded during device startup.

Limitations

• In hot standby scenarios in load balancing mode, ensure that the incoming and outgoing paths of the packets are the same. Otherwise, the FW cannot perform mail filtering detection.
• Mail filtering does not support IPv6.
• Mail filtering does not apply to Exchange mails.
• To enable mail filtering for SMTPS, POP3S, or IMAPS traffic, configure SSL-encrypted traffic detection. For details, see configuration examples in SSL-Encrypted Traffic Detection.
• Mail filtering based on MIME headers does not support filtering of Chinese aliases of senders, recipients, and copy-to persons. When the MIME header field name (field-name) in the MIME header filtering rule is set to From, To, or CC, the corresponding field value (field-body) cannot contain Chinese characters.
• When the MIME header field name (field-name) in the MIME header filtering rule is set to Subject, the corresponding field value (field-body) supports Chinese characters encoded using GB2312 and UTF8.
• The FW does not support mail filtering when it functions as a bypass detection device.
• In a virtual system, the FW does not support spam filtering in mail filtering.

Precautions

If the FW is deployed between two routers, and the routers detect each other through BFD, you are advised to properly prolong the BFD time (longer than 100 ms is recommended) to prevent BFD flapping resulting from occasional network congestion.