Compiling postfix (1.,1,11-r1) with SASL (cyrus-sasl 2.1.5-r1) support doesn't work as expected. It fails when trying to link because of it cant find -lsasl. I've checked my system and found out that I dont have -lsasl but I have -lsasl2. I hacked the ebuild and replaced -lsasl with -lsasl2 and I got to a point where it couldnt find sasl.h, so I added /usr/include/sasl also. Now it seems like -lsasl2 isnt backward compatible with -lsasl so the build breaks anyway. I notice this as a major bug because SASL is needed for SMTP AUTH and that's very importand when hosting virtual mail-servers where users need to connect from untrusted IPs.
postfix-1.1.11.20020613 which is currently in portage fixes this problem.