Why can I use BerkeleyDB 4.1.x?
SleepyCat changed the API from Berkeley DB 4.0 to 4.1. Hence it is not supported in sendmail 8.12.6. Moreover, the semantics of the open() call have been changed, hence sendmail doesn’t work with DB 4.1.x (x <= 24), even if the "obvious" API changes are made. However, with the release of Berkeley DB 4.1.25 and sendmail 8.12.7, things should work again with these versions (or greater, when the time comes).