As mentioned previously I have switched from using the gld greylisting implementation to policyd . I had originally used the version of policyd in the ubuntu apt repositoriesmainly for ease of installation and maintenance. After reading the policyd mailing list it became very clear that it would be of great advantage to upgrade from the modest v1.55 release in the repository to the latest- v1.73. There are quite a few new features in v1.73 compared to v1.55:
HELO check blacklist hosts which use a random HELO
DNS based whitelists
Blacklist sender (envelope)
DNS based blacklisitng
SSL and Compression on MySQL connection
I cleanly removed v1.55 with apt-get remove; v1.73 compiled with no problems. One thing to remember is that while the README.txt tells you to use gmake, you in-fact substitute this command with make on a Ubuntu system.