Filtering of Incoming Email on the Mail Server

Metropolia filters email to combat spam, viruses, and malware. All checks related to filtering are performed by the mail gateway before an email is accepted for further delivery.

Prohibited File Types

The following file types are not accepted:

• .pif
• .scr
• .exe
• .vbs
• .cpl

These files must be packed, for example, into a zip archive. 

Blacklists

Metropolia does not accept email from servers that are on certain blacklists. The lists currently in use are:

• sbl-xbl.spamhaus.org
• bl.spamcop.net

Greylisting

Metropolia uses greylisting technology to block spam sent via botnets. You can read more about this technique in the Ministry of Transport and Communications’ spam information package.

Antivirus

All incoming and outgoing messages are scanned for viruses. Messages containing viruses will not be forwarded.

Spam Sorting

Incoming messages are automatically analyzed by the SpamAssassin program. Based on this analysis, a rating is added to the message headers indicating how likely it is to be spam. These headers can be used to sort spam messages into their own folder.

The headers of a message suspected to be spam look, for example, like this:

X-Spam-Flag: YES
X-Spam-Score: 6.919
X-Spam-Level: ******
X-Spam-Status: Yes, score=6.919 tagged_above=-9999 required=5	tests=[HTML_MESSAGE=0.001, ...

The X-Spam-Status header shows on what grounds the message has received its score; a more detailed explanation of the criteria can be found on the SpamAssassin website.

It's recommended to create a spam filtering rule in Outlook Web Access so that it works even when Outlook is not running. Create the rule as follows:

• Click the gear icon in the upper right corner, then select Settings
• On the left, select Inbox and sweep rules
• Create a new rule by clicking (+)
• Give the rule a name
• In the upper menu, select:
  
  • When a message arrives, and it matches all of these conditions
  • It includes these words
  • in the message header...
  • X-Spam-Status: Yes
• In the lower menu, select:
  
  • Do all of the following
  • Move, copy, or delete
  • Move the message to folder...
  • and choose the Junk E-mail folder
• Check the box "Stop processing more rules"
• Click OK

The completed rule will look like this:

Spam messages still gets through

Spam filtering is managed in such a way that legitimate messages are not filtered. It is inevitable that some spam will get past the filter at the same time. If you receive a lot of spam, you can send samples of them to the helpdesk. We can try to improve the filtering based on those, but it may not necessarily succeed.

The message must be forwarded with headers so that the transmission data is preserved.

You can send the messages to us as attachments according to these instructions:

How do I attach a received message to a service request?

Roskapostin suodatus