SENDER AUTHENTICATION FOR DIFFICULT TO CLASSIFY EMAIL
First Claim
1. A method for authenticating a received email used by an email system, comprising:
- classifying the received email as either a first type or a second type based on whether the sender domain of the received email is associated with a spammer,when the received email is classified as the first type, sending a first type of bounceback email with a new sub-address to a sender of the received email, the first type of bounceback email having the new sub-address in computer-readable form, the new sub-address being appended to the origination email address in the bounceback email, andwhen the received email is classified as the second type, sending a second type of bounceback email to a sender of the received email, the second type of bounceback email having a test in a body of the second type of bounceback email, the test for differentiating a human from a machine and having a solution that is the new sub-address,wherein a destination address of a reply-to-bounceback email includes the new sub-address.
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Accused Products
Abstract
The portion of email traffic that cannot be definitively determined to be spam or definitively determined to be ham (non-spam) is processed by sending a bounceback email to the sender, requiring the sender to reply using a sub-address created by the bounceback generator. The type of bounceback email depends on whether the domain of the received email indicates that the sender is or is not likely to be a spammer. When the sender is not likely to be a spammer, the bounceback email includes a sub-address in computer readable form. When the sender is likely to be a spammer, the bounceback email includes a test that must be solved to yield the sub-address; preferably, the test is very difficult for a computer to solve but reasonably easy for a human to solve. When a reply email to the bounceback email (“reply bounceback”) is received, the presence of the sub-address indicates that the sender is not a spammer, so the reply bounceback is determined to be ham and delivered to the destination mailbox. The bounceback can have the sub-address encoded in such a way that a human must be involved in decoding, which is appropriate for situations where the envelope sender domain of the original email is considered suspicious. The bounceback can have the sub-address presented in a computer readable format when the envelope sender domain of the original email is more trustworthy, if authenticated. Authentication information can be retained in a local private Sender Policy Framework (SPF) database, or shared in a centralized private SPF database.
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Citations
23 Claims
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1. A method for authenticating a received email used by an email system, comprising:
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classifying the received email as either a first type or a second type based on whether the sender domain of the received email is associated with a spammer, when the received email is classified as the first type, sending a first type of bounceback email with a new sub-address to a sender of the received email, the first type of bounceback email having the new sub-address in computer-readable form, the new sub-address being appended to the origination email address in the bounceback email, and when the received email is classified as the second type, sending a second type of bounceback email to a sender of the received email, the second type of bounceback email having a test in a body of the second type of bounceback email, the test for differentiating a human from a machine and having a solution that is the new sub-address, wherein a destination address of a reply-to-bounceback email includes the new sub-address. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23-33. -33. (canceled)
Specification