It's not supposed to accept long addresses. It is POP3 protocol limitation: an argument for a command should not be more than 40 chars.
Commands in POP3 consist of case-insensitive keywords, possibly
followed by one or more arguments. All commands are terminated by a
CRLF pair. Keywords and arguments consist of printable ASCII
characters. All keywords and arguments are separated by a single
SPACE character. Keywords are three or four characters long. Each
argument may be up to 40 characters long.
However you should be able to read E-mail using IMAP servers.