Rmilter now can sign mail that come from certain networks as well.
86 karma · joined October 21, 2014
Both systems support statistics (rspamd uses 5-gramms hidden Markov model and SA uses naive bayes), they both support different backends for statistics (redis and sqlite for rspamd), per-user statistics, autolearning. Among network checks, they support URIBLs, RBLs, DMARC, DKIM, SPF. Obviously, both systems support regexp rules. However, I'm not an expert in SA features and might thus miss something...
In brief, rspamd can use the most of SA rules but it provides more optimization tricks than SA does. However, it is less mature and could be harder to setup than SA. You can also check my recent FOSDEM talk: https://www.youtube.com/watch?v=_fl9i-az_Q0
I'm really sorry that this information is not in the landing page of rspamd.com - that's obviously my fault.
Regarding statistics, rspamd uses OSBF-Bayes classifier and 5-gramms input (so it is not naive bayes). I've used the following academic paper: http://osbf-lua.luaforge.net/papers/osbf-eddc.pdf as reference. This algorithm is also used for crm114 spam classifier. However, bayes classifier is a very small part of rspamd (unlike dspamd, for example) and it could be almost useless if you have, let's say, 50 millions of users accounts. Rspamd is targeted for this grade systems.
Multiple database drivers are in plans for rspamd 1.0 (along with personal statistics and advanced rules planner). The tricky stuff here is that rspamd uses non-blocking model currently which is hardly supported by database drivers (excluding redis and some others). However, rspamd has a concept of asynchronous threads executed in thread pool. So something like MySQL query could be executed within this thread pool with no delay for other filters processing.