I built cyrus-sasl from source code, since I need SQLite support, but not mysql/pgsql ... so, I try 'apt-get install postfix', since I figure that mysql/pgsql won't hurt there, and I don't need any other features that really require me to build it custom ... but, apt-get comes back with:
Given Aurelien just rebuilded and uploaded postfix_2.3.7-3+kbsd, please do "apt-get update" against ftp.gnuab.org now. Previously have been postfix_2.2.8-9+kbsd uninstallable. In fact, you have now two options. a) Use .deb for all packages, including cyrus-sasl. Just try again "apt-get install libsasl2-modules-sql postfix". It should work now. b) still use own cyrus-sasl 2.3 I do not know whether libsasl2 from 2.3 is ABI compatible with 2.2.If it is ABI compatible, it would be sufficient to just create .deb from cyrus-sasl 2.3 or use "equivs" package to satisfy dependencies.
If it is ABI incompatible, but API compatible, you have to rebuild postfix against your version of libsasl2 in any case. Petr