Grey Listing

Anti-spam / Anti-virus technology.

Special service for system managers/post masters: Do you receive error messages from our mailservers? We can help you configure your mailserver, to prevent problems in the future.

Cyso Managed Hosting uses a number of proven techniques to defend against SPAM and VIRUSES.

Greylisting.

Greylisting is a new but widely accepted way to fight spam. We use three different pieces of information (triplet) from the e-mail consisting of:

• Sending mailserver's IP
• Sender's adress
• Receiver's adress

Every time a new unique triplet is offered to our mailserver, the email is sent back to the sending mailserver, requesting a resend in a few minutes. If this happens within the next few hours, this email will be delivered and will always be directly delivered for this unique triplet.

Most of the spam is sent by mailservers that won't resend the email, so it never reaches its destination.

For more information visit: http://projects.puremagic.com/greylisting/ of: http://www.greylisting.org/.

Adress verification.
After greylisting, we check if the receiver is a "real adress". If this isn't the case, we send an error message back to the sender. We use this technique to keep our servers fast, reliable and to alleviate server load.

Antivirus / Spamassassin
After these two steps we check the email with 2 separate virus scanners and an anti spam machine. We check the mail for viruses and spam. If a virus is found, the email will automatically be cleaned or be deleted. The user will automatically recieve a notification. If a message is suspected to be spam the headline of the message will be changed to add the heading: Spam?

You can filter these messages automatically by creating rules in your email application.

We also check for certain file extensions and filenames. If they are 'suspect' these files will be blocked by our servers.
These files are:

• Executables: .exe .bat .com.
• Files that pose a threat to Microsoft Windows (also read Microsoft Knowledgebase article Q883260): .its .mau .md .vsm macros.
• WinEvar virus attachment: .ceo.
• I-Worm.Yanker virus attachement: webpage.rar.
• Filenames consisting of more than 150 characters.
• Filenames with too many spaces.
• Masked filenames: extensions consisting of more than 25 characters.

Blocked files are always recoverable via our lost mail functionality. A notification will be sent, containing all information how to retreive the file(s) using a webinterface.

Non RFC compliant mailservers

Although our servers comply to all standards, some (poorly configured) mailservers don't react to certain messages by our mailserver. Our policy is to keep these servers at a distance, because they increase the risk of spam. We can make exceptions for certain servers or domains and whitelist them. We will only do this if absolutely neccesary.

Our mailservers comply to specifications mentioned in RFC 821 (aug 1982), RFC 1891 (jan 1996), RFC 1893 (jan 1996), RFC 2821 (apr 2001) en RFC 3463 (jan 2003).

Would you like to know more about this subject? Contact us at: greylisting @ adm.cyso.net*

* No greylisting is used at this adress, mail from all servers wil arrive.

Active viruses

This report is generated live by our spamfilters.