Trend Micro Email Security (TMEMS) Inbound Protection users could not receive some Microsoft Office 2007 or 2010 attachments being sent to them. The Mail Tracking logs show that the mail was "Bounced".
Trend Micro Email Security Inbound Protection has the following global limits:
- Total message size exceeds:
- TMEMS Standard: 50 MB
- TMEMS Advanced: 150 MB
- Total number of recipients exceeds: 1000 recipients
- Total number of embedded layers in compressed file exceeds: 20 layers
- Size of a single decompressed file exceeds: 60 MB
- Total number of files in compressed file exceeds: 353 files
- Compress ratio limit exceeds: 100%
- An Office 2007/2010/2013/2016 file contains more than 353 subfiles.
- An Office 2007/2010/2013/2016 file contains a subfile whose decompression ratio exceeds 100.
By nature, Microsoft Office 2007 or 2010 files (e.g. .XLSX, .DOCX, .PPTX) are zipped files. When scanning, TMEMS scan engine treats these files as ordinary zip files and applies the same scan settings for compressed files. The file number within these files is uncertain, so these files may sometimes violate compressed file scanning exceptions.
To resolve the issue, do one of the following:
Option 1. Password-protect the MS Office attachment
Ask the sender to password-protect MS Office 2007/2010/2013/2016 attachments. By doing this, scanning of these files are bypassed.
Option 2. Modify the action for MS Office attachment
TMEMS users can modify the action that it may take on MS Office 2007/2010/2013/2016 attachments from Reject to Bypass:
- Log in to the Trend Micro Email Security portal.
- Go to Inbound Protection > Virus Scan > Scan Exceptions.
- Click the configured Action on the right side of "An Office 2007/2010/2013/2016 file contains more than 353 subfiles" setting.
- Under Intercept section, select Do not intercept messages.
Configure the Modify and Monitor actions as necessary.
- Click Save.
For more information, review these online help documents: