The db(3) form of database uses a single file and can be shared by different architectures. If you intend to support aliasing in an efficient manner, you should at least define this NEWDB (or the NDBM described earlier) in your Build m4 file. The db(3) routines are used to look up aliases and are the routines used by the User Database (See this section). They can also be used to declare hash and btree type maps (Section 23.2.2) with the K configuration command.

The db(3) libraries have overcome many of the limitations of the earlier ndbm(3) libraries. If possible, you should get and install the db(3) libraries before you build sendmail (see Section 3.1.2 for a guide to downloading these libraries).

If you are running a precompiled sendmail binary, you can use the -d0.1 debugging command-line switch (-d0.1) to determine if NEWDB support is included (if it appears in the list, support is included).