Limit connections to minute via ipf?

[fuser9bb at HotPOP.com]

I'm using Postfix and would like to artifically limit incoming connections
per minute to a certain value. We have ipf available. Postfix can be
configured to limit concurrent connections, but not connections per minute.
Has anyone gotten something like this working well with ipf? Pros/cons?

I am using FreeBSD 4.9.