2.2.9 [RFC1939] Section 7, PASS Command

C0010:

The specification states: "When the client issues the PASS command, the POP3 server uses the argument pair from the USER and PASS commands to determine if the client should be given access to the appropriate maildrop."

Microsoft Exchange Server 2007

If the user is not in the same site as the Client Access server to which the client is connected, Microsoft Exchange Server sends a login failed error to the user.

V0011:

The specification states: "Since the PASS command has exactly one argument, a POP3 server may treat spaces in the argument as part of the password, instead of as argument separators."

Exchange 2007, Microsoft Exchange Server 2010, Microsoft Exchange Server 2013, Microsoft Exchange Server 2016, Microsoft Exchange Server 2019

Microsoft Exchange allows unquoted spaces in the PASS argument, and uses the entire remainder of the command as a single password argument.