Currently there is a choice between sending an email on the delta or sending an email with every build.

The every build option is too noisy... but sending on delta can mean that, e.g. the broken build status gets lost.

It would be great if there was an option to send every Nth build. Thus you could configure like so:

Successful builds: on transition to successful and every 50th build
Unstable builds: on transition to unstable and every 10th build
Failed builds: on transition to failed and every build

That would mean that while the build is stabled you do not get spammed, but you get a periodic heartbeat to let you know that the build is still there doing its job of checking the code.

When a test breaks, you get periodic reminders that the test needs fixing... but you are not drowned in them.

When the build is broken you get blasted with emails until you fix it.

Another option (though perhaps harder to implement) would be to limit the number of emails in any category to at most N per day/week/month