[Dovecot] pop/imap login logging only username part of full email address

I have my login log format set like so:

login_log_format_elements = user=<%u> method=%m rip=%r lip=%l %c

When I log in using a full email address, though, I only get the username part of the address:

Jan 24 13:28:29 node7 dovecot: pop3-login: Login: user=<justin>, method=PLAIN, rip=137.118.2.60, lip=137.118.7.247 Jan 24 13:28:30 node7 dovecot: POP3(justin): Disconnected: Logged out top=0/0, retr=0/0, del=0/717, size=15797460

Is that behavior intentional? If so, can it log the full username as given by the client instead? Anyone with multiple domains probably wants to see the domain part. Changing %u to %n yields the same log entry, and %d seems to be empty so nothing gets logged if I try to log that.