I put together a new SpamAssassin rule that will help identify spam from spoofed email addresses.
Some email providers always sign email with DKIM or DomainKeys … based on this assumption, if you get a message from one of those domains and it isn’t signed, you can assume its more likely to be spam.
This particular rule operates on the assumption that all mail from Yahoo & Gmail will be signed. It does not, however, raise the score a huge amount … because it’s just more LIKELY to be spam if it’s not signed … it’s not guaranteed to be spam. Some people may use the Yahoo or Gmail account’s in the from address, but not actually send from that service.
I saw a very interesting mail reject message today on one of my mailing lists …
You are receiving this message because you have attempted to send an e-mail containing confidential information. Examples of confidential information include, but are not limited to social security numbers, birth dates, account numbers, policy numbers, medical history, financial history, personal phone numbers and user IDs. Another example of sending confidential information would be combining any two or more of the following: name, address, identification numbers (employee number, phone number), organizational affiliation (place of employment). This information may be contained in the body of the message or any attachments.
I looked at the body of the message it was rejecting (which was included in it’s entirety), and noticed that the message referenced dummy social security numbers (the message discusses SQL techniques).
Of course, based on the warning message, it would probably reject ANY numeric text that was included in a message at all.
I suspect that the company, who’s server rejected the message, does not have a problem with email volume … since the majority of email sent to them is probably rejected.
I really wonder about companies that have such incredibly draconian content rules. How do they stay in business?
Here are a few things that I recommend for folks who use PC’s … think of them as “David’s Rules for PC Owners” …