That's good. Nothing I have done tries to accommodate a user logging in to webmail via an IP address.
Just curious, what is the output of this command:more /home/httpd/html/horde/imp/config/backends.local.php
I'm going to guess that $servers and maildomain says domain.local since that is what your first entry shows in the conf-auth-admins array.
If you could have logged into webmail using the domain.local fqdn, then I suspect this would have worked for you with no issues.
I don't know if there is a real fix for logging in via IP address and wanting to show the admin options. If there is, the code for that is above me.
I also use an fqdn and it just works for me.
If you try to switch to test, then your admin preferences will be reset because nothing will have been saved for admin@domain.local, only for admin@0.93.
Sorry for coming to the party late, I got your email, then tried to respond by my smarthost is/was being blacklisted by one of the rbl's you are using, then I tried to respond directly via my gmail account, but I never got a response whether you received that or not. Clicking on the horde icon was my next suggestion to see what horde was showing as your user credentials.
John