Chronophage.net Blog

Postfix is surprisingly flexible. When I initially set it up two years ago, I set it up to reference a database, but I had a flaw in my logic. Basically, Postfix had no idea if a domain was marked active or inactive in the database. All it knew was whether a domain was in the database or not. Postfix has a default query, that looks for key information. However, you can supercede it in your config files. So I simply commented out the old variables that it passed to the default query, and wrote a new one:

user = DB_USER
password = supersecretpassword
hosts = 127.0.0.1
dbname = DB_NAME
table = domain
#select_field = domain < -- old version, commented out
#where_field = domain <-- old version, commented out
#New Query:
query = SELECT domain FROM domain WHERE domain='%s' and backupmx = false and active = true

Yes, I have backupmx enabled, even though that’s a titanically bad idea, and I would never use it. Why is it a bad idea to fuction as a Backup MX server? Because spammers don’t play by the RFCs and often send spam to lower weighted MX records in an attempt to bypass spam protection.

But I never know what people may ask for in the future.