Session Limits:_ These settings limit the number of concurrent sessions accessing this Account. If the number of the already opened sessions exceeds the specified limit, a new login operation is rejected with an error code being sent to the client application.
POP Login Limit: This setting limits the frequency of POP Logins into this Account. If the number of POP logins exceeds the specified limit, the session is rejected with an error code being sent to the mail client. The user should change the POP client settings to make it check mail less often.