My suggestion:
Warning: Bitcoin transactions are designed to be permanent. Scams happen, and are not moderated on this forum. Be very careful who you trust.
Will this be sent to a new account instantly? That's what happens when I open a new Gmail account, I think it sends me even 3 emails at once. And that's not the first thing I'm going to read when I've created a new account.
My suggestion would be to either send it in parts, or send the same message again as a reminder once the user has made a few posts.