I just joined and have been reading some old posts. Someone mentioned that you need to make 5 posts before you can use private messages.
Another claims you are limited to one post a day.
Where can I find these rules and perhaps others?
Yes you must make 5 posts before you can send PMs. We have had problems with folks joining up just to harass members via PM. The five message rule is to encourage people to engage in the community before sending PMs.
You are not limited to one post per day. I have no idea where this came from.
However, I believe Posts and PMs are limited to a certain number per hour. (Or you will get a message that you can not send/post another so soon after sending a first) This limitation is imposed by the forum software. This is is to prevent spammers from flooding everyone's mailboxes or the board with ads for Viagra.