A method, an apparatus, and a device for detecting an E-mail attack. The device receives a data flow; obtains an E-mail traffic parameter of each statistic period within a predetermined number of statistic periods, where within each statistic period, the E-mail traffic parameter of each of the statistic periods is determined according to a protocol type of the received data flow; and determines that an E-mail attack is detected when the E-mail traffic parameter of each statistic period within the predetermined number of statistic periods matches a first threshold. By applying the disclosed embodiments, a detection result of the E-mail attack is more accurate.