I am receiving the following SMTP error:
"550 Virus Oversized.Zip detected. Mail delivery avoided"
- On-Premise Server + WebMail Installations: Version 6.0 > Current Version
This is due to the ClamAV engine of Atmail scanning a message attachment and the zip file compression ratio is too high. For example, zipping a large number of BMP files with high compression.
This feature is implemented in ClamAV to avoid a special crafted Zip file to loop on extraction causing a denial-of-service attempt.
To change the compression ratio simply edit: /usr/local/atmail/av/etc/clamd.conf
# If a file in an archive is compressed more than ArchiveMaxCompressionRatio # times it will be marked as a virus (Oversized.ArchiveType, e.g. Oversized.Zip) # Value of 0 disables the limit. # Default: 250 ArchiveMaxCompressionRatio 0
Specify 0 to disable, or increase the ratio above the default 250, then restart the Atmail services.