I'm a mostly-Windows guy tasked with setting up email on an Ubuntu 12.04 instance at AWS and hit the following error:

When I browse to Horde, after entering my administrative credentials, I get the error message:

A fatal error has occurred

imp is not activated.

Details have been logged for the administrator.

I am following the following, quite detailed guide

http://www.exratione.com/2012/05/a-mailserver-on-ubuntu-1204-postfix-dovecot-mysql/

This is happening at Step 20, at the text Now fire up you web browser and navigate to your server at http://mail.example.com/ to verify that you can log in as the configured administrative mail user. (of course I used my actual domain).

Questions

• Where is Horde logging the "details"?
• Any thoughts on why this might happen? I found Google hits suggesting that php5-mcrypt might be missing, but I verified it is installed and up-to-date in my case.