17. A system for detecting graymail without explicit user feedback, comprising: a data analytics computer system, comprising: a processing element; and a memory, coupled to the processing element, on which is stored software for predicting whether a user would consider an email graymail, comprising instructions that when executed cause the processing element of the data analytics computer system to: receive a non-spam email for a user; extract features of the email; predict with a classifier model based on the extracted features whether the user would consider the email as graymail; and train the classifier model responsive to tracked user actions; and a tracking engine computer system, comprising: a processing element; a tracking database; and a memory coupled to the processing element, on which is stored software for tracking user actions on the email, comprising instructions that when executed cause the processing element of the tracking engine computer system to: modify the email by inserting tracking information before delivering the email to the user; storing the inserted tracking information in a tracking database; track user actions on the email without explicit user feedback using the inserted tracking information; update the tracking database upon detection of tracked user actions on the email; determine whether the user considered the email as graymail responsive to the tracked user actions without explicit user feedback; and provide information regarding the determination to the data analytics computer system for training the classifier model.
17. A system for detecting graymail without explicit user feedback, comprising: a data analytics computer system, comprising: a processing element; and a memory, coupled to the processing element, on which is stored software for predicting whether a user would consider an email graymail, comprising instructions that when executed cause the processing element of the data analytics computer system to: receive a non-spam email for a user; extract features of the email; predict with a classifier model based on the extracted features whether the user would consider the email as graymail; and train the classifier model responsive to tracked user actions; and a tracking engine computer system, comprising: a processing element; a tracking database; and a memory coupled to the processing element, on which is stored software for tracking user actions on the email, comprising instructions that when executed cause the processing element of the tracking engine computer system to: modify the email by inserting tracking information before delivering the email to the user; storing the inserted tracking information in a tracking database; track user actions on the email without explicit user feedback using the inserted tracking information; update the tracking database upon detection of tracked user actions on the email; determine whether the user considered the email as graymail responsive to the tracked user actions without explicit user feedback; and provide information regarding the determination to the data analytics computer system for training the classifier model. 22. The system of claim 17 , wherein the instructions further comprise instructions that when executed cause the processing element of the data analytics computer system to: store the extracted features in a database.