Methods, systems, and devices are provided for detecting spam filtering. According to one aspect, the system can inject, by a server, into a client email campaign a plurality of emails for transmission to a plurality of seed email addresses separate from a plurality of non-injected emails of the client email campaign for transmission to a plurality of target email addresses. The system can detect whether the one or more injected emails were categorized as spam or not spam by each of the plurality of seed email addresses and generate a first input to an analysis module. The system can monitor a plurality of sensing signals from the non-injected emails and generate a second input to the analysis module. The analysis module can predict based on the first input and second input whether the non-injected emails are categorized as spam by the target email addresses.