search for: duserdb_vpopmail

...$prefix/lib/dovecot/auth/ directory. Binary packages builders should use them for authentication modules which require external libraries (e. g. LDAP and vpopmail). There is no standard way to build them as modules currently, but something like this should work: gcc -shared -fPIC -DHAVE_CONFIG_H -DUSERDB_VPOPMAIL -DPASSDB_VPOPMAIL \-I../.. -I../lib userdb-vpopmail.c passdb-vpopmail.c -o vpopmail.so \-lvpopmail I had to modify the command to build the module, but was able to successfully build it: gcc -shared -fPIC -DHAVE_CONFIG_H -DUSERDB_VPOPMAIL -DPASSDB_VPOPMAIL -I../.. -I../lib -I/home/vpopmail/include...