Newbie can send PM, but it depends if to whom a newbie want to send to like if the user (higher ranks) don't allow to get a message from newbies, here's a thread^[1] how it is explained.

I don't know where you get the idea of getting 30 posts can make newbie to send a message. But Im thinking its because a newbie might become jr member already by making 30 posts, but that was before everything was change after merit implementation^[2].

If you want to send PMs like with a member restrictions, probably can send with shorter time limit than newbie and jr member, then paying for copper membership is your option^[3].

[1] https://bitcointalk.org/index.php?topic=2728840.0
[2] https://bitcointalk.org/index.php?topic=2818350.0
[3] https://bitcointalk.org/index.php?topic=2385104