There is a new version of courier
I've renamed the 0.70 ebuild to 0.71 and it seems to work perfectly fine (on x64).
There is now a new development build courier-0.71.20130913 which includes the following changes: • Include userid of failed SASL authentication requests in mail logs, if available. • By popular request, new ratefilter module, implements per-sender rate filtering.
has been committed without closing this bug