Trouble with virtdomains

[ogjunk-cyrus at yahoo.com]

Hello,

I'm trying to configure Cyrus IMAP (cyrus-imapd-2.2.6-2.FC3.6 - Fedora
Code 3 package) to serve multiple domains.  I have it accept email from
Postfix when I don't use multiple (virtual) domains, but not with
"virtdomains: yes" in /etc/imapd.conf.

Here is what I have in /etc/imapd.conf:

... <standard stuff taken out> ...
sasl_pwcheck_method: saslauthd
sasl_mech_list: PLAIN
tls_cert_file: /usr/share/ssl/certs/cyrus-imapd.pem
tls_key_file: /usr/share/ssl/certs/cyrus-imapd.pem
tls_ca_file: /usr/share/ssl/certs/ca-bundle.crt

# OG: added
virtdomains: on
defaultdomain: my-domain.com
unixhierarchysep: 1
loginrealms: localdomain my-domain.com

If I comment out the last 3 lines, then I _can_ create new mailboxes
with cyradm (e.g. createmailbox user.otis.Trash).  However, I need this
server to serve email for multiple domains, so I need to be able to do
"cm user/otis at my-domain.com")

I've followed this:
  http://asg.web.cmu.edu/cyrus/download/imapd/install-virtdomains.html

But that results in this:

  cyradm -u cyrus localhost 143
  IMAP Password:
  localhost.localdomain> cm user.otis at my-domain.com
  createmailbox: Invalid mailbox name

I also tried this:

  localhost.localdomain> cm user/otis at my-domain.com
  createmailbox: Invalid mailbox name

I presume that's because Cyrus doesn't know about "my-domain.com".  How
do I tell it about "my-domain.com"?

I also read this:
  http://www.phildev.net/cyrus/cyrus_sasl.html

But that had a few errors, so I gave up around half of the job. 
Perhaps Cyrus and cyradm would know about "my-domain.com" if I called
cyradm like this:

  cyradm -u cyrus my-domain.com 143

?
I tried that, but my-domain.com domain is not really configured yet
(DNS points to a different, old machine), so I can't really try that.

Any help would be appreciated.

Thanks,
Otis
P.S.
Similar thread is here, but this doesn't seem to work for me:
http://asg.web.cmu.edu/archive/message.php?mailbox=archive.info-cyrus&msg=35013

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