Superceded by request #10764 for Ingo 2.

From my original email to the horde mailing list:

We have one Horde front-end for multiple domains. The user selects the
domain on the login page and is authenticated by the selected back-end
IMAP server. All of this works fine. But in Ingo, the "My Email
Addresses" field defaults to just the username with no domain. The
script can not be activated without the domain included in the
address.

I can set the address with the proper domain by using
$conf['hooks']['vacation_addresses'] = true; and using the following
hook script

if (!function_exists('_ingo_hook_vacation_addresses')) {
     function _ingo_hook_vacation_addresses($user = null)
     {
         return array($user . '@' . $_SESSION['imp']['maildomain']);
     }
}

The problem is that even with $conf['hooks']['vacation_only'] = false;
only the address generated by the hook is getting saved. The user can
enter a different or additional addresses, but they are not saved nor
are they entered into the script.

-- end original message to list

It is my understanding that setting ['hooks']['vacation_addresses'] = 
true and ['hooks']['vacation_only'] = false is intended to pull the 
default address(es) from the hook, but still allow the user to modify 
as needed.

However, in my tests the only address that was saved with the vacation 
filter was the one generated by the hook.

My workaround was to use the from_addr hook. With the from_addr 
properly set, I disabled the vacation_addresses filter. The vacation 
filter will use the from_addr by default and then the user can also 
edit the addresses as needed just for the filter.