Post Office Protocol is an application-layer Internet standard protocol used by local e-mail clients to retrieve e-mail from a remote server over a TCP/IP connection. POP has been developed through several versions, with version 3 (POP3) being the current standard. Virtually all modern e-mail clients and servers support POP3, and along with IMAP they are the two most prevalent Internet standard protocols for e-mail retrieval. This test suite can be used for robustness testing of POP3 Server implementations.