Yes. Make sure AUTHMODULES in /etc/courier-imap/{imapd/pop3d} are set to "authvmailmgr authdaemon" and that the "real" domain is added to "/etc/qmail/control/locals". It is also worthy of mention that an "elvis" must be a virtual user.
Look in /var/log/maillog. See if there is something like this:
deferral: Connected_to_IPADDR__but_my_name_was_rejected. /Remote_host_said:_501_5.0.0_HELO_requires_domain_address/
If you see a line similar to that in maillog, it means that qmail package couldn't figure out what your fully qualified domain name was during installation. The situation is easy to remedy, though. Do the following:
cd /etc/qmail/control
echo my.host.name > me
echo my.host.name > plusdomain
echo my.host.name > defaultdomain
You should also check and make sure that my.host.name is in rcpthosts and locals. Naturally, you need to substitute my.domain.name for something actually relevant.
Run /etc/init.d/qmail restart after you've done these modifications.