[Dovecot] Filtering attachements ?

[Stan Hoeppner]

Timo Sirainen put forth on 3/12/2011 7:13 AM:
> On Tue, 2011-03-08 at 17:42 +0100, Frank Bonnet wrote:
> 
>> Is there a way to filter some attachments with dovecot ?
> 
> I think there are some generic IMAP tools for that..

What kind of attachments?  Viruses or just annoying things like .vbs,
.bat, stuff that a/v programs don't reject?  Do you want to reject the
emails or strip the attachment off and delivery the email?  You can
reject emails that contain arbitrary attachments easily with standard
Postfix, for example:

/etc/postfix/main.cf
...
mime_header_checks = pcre:/etc/postfix/mime_header_checks
...

/etc/postfix/mime_header_checks
# Reject email containing unwanted attachments

/name=\"(.*)\.(386|bat|chm|cpl|cmd|com|do|exe|hta|jse|lnk|msi|ole)\"$/
        REJECT Unwanted attachment $1.$2
/name=\"(.*)\.(pif|reg|rm|scr|shb|shm|shs|sys|vbe|vbs|vxd|xl|xsl)\"$/
        REJECT Unwanted attachment $1.$2


You may also use any access table action instead of REJECT, such as
DISCARD, WARN, etc.  You could even pipe an offending message to an
external content filter when one of these attachments is found, using
the FILTER action and have the external daemon strip the attachment.

-- 
Stan