POP3
This signature detects Post Office Protocol (POP), which is an application layer Internet standard protocol to retrieve e-mail from a remote server over a TCP/IP connection. It is one of the most prevalent Internet standard protocols for e-mail retrieval. POP3 server usually runs on TCP port 110.
Available to all SRX running 12.3X48+
Available to all MX running 20.2R1+
Available to all vSRX running 20.3R1+