[Dovecot] Building the Antispam plugin fails

[Michael Neurohr]

Hi!
I'm running Dovecot 2.2.5 on a CentOS 6.4 server from the ATRPMs
repository. Unfortunately this repo does not provide a packaged version of
the Antispam Plugin.

So I followed the steps outlined in the Dovecot Wiki [1].
But when running the command ./configure, I get stuck with the following
error:

checking for dovecot-config in "/usr/local/lib/dovecot"... not found
configure:
configure: Use --with-dovecot=DIR to provide the path to the dovecot-config
file.
configure: error: dovecot-config not found

So I downloaded the dovecot-devel package and run the configure command
again with the following command:
./configure --with-dovecot=/usr/include/dovecot
but with the same result.
I made sure the the directory "/usr/include/dovecot" does contain the
Dovecot header files.

What can I do next? Do I really also have to install Dovecot from the
sources only to get the Antispam Plugin working?

Thanks,
Michael

[1] http://wiki2.dovecot.org/Plugins/Antispam