[Dovecot] USER environment missing

I am new to dovecot, and while I have the pop server running fine, I am having trouble with the imap server.

It starts, but when I try to connect, I get an error:

telnet localhost imap Trying 127.0.0.1... Connected to localhost.localdomain. Escape character is '^]'. imap(??): Fatal: USER environment missing Connection closed by foreign host.

Not sure where to start on this one. (or what to show you).

I am running under Ubuntu Linux, usiang postfix, fetchmail, etc.. (not sure that matters).

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