Content blocked due to source IP characteristics

The message contained an attachment capable of propogating malware such as a Word or Excel document, while coming from a source that appears to be a commodity, consumer-grade, or unassigned IP address rather than from a regularly set up mail server. This makes it look like an attack by a botnet.

For this purpose, an address is judged to be "commodity" if it has an associated name which has the address encoded in it plus some other factors, so the name typically looks something like "44-33-22-11.mytelco.com".

It is considered "unassigned" if it has no name associated with it at all. If your mail server is running on an address that looks like this you might consider having your ISP associate it with a specific name like "mail.mycompany.com".

If you are unable to register your mail service in the DNS with assistance from your ISP, or you believe we have made an error in judging your address not to be a valid email source, then please contact postmaster@ed.ac.uk.