MAMP problem receiving email

Since short I have a problem with MAMP that doesn’t let WordPress send emails to me.

For example:
When I add a new user, that user will get an email with all the details, but the emails aren’t send.

I tried to use MAMP Pro, but no difference.
It worked before and I also tried to use Snow Leopard itself, but when I create a new Blog with WordPress I don’t get the email (confirmation that you started a blog).

When I look in the Terminal it tells me I’ve got mail. I can view the mails and those are the mails that couldn’t be send.

Message-ID: <2da20138410b064a1bce8640741b4e69@localhost>
X-Priority: 3
X-Mailer: PHPMailer (phpmailer.sourceforge.net) [version 2.0.4]
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Content-Type: text/plain; charset="UTF-8"

Your new WordPress site has been successfully set up at:

http://localhost:8888/link from site

You can log in to the administrator account with the following information:

Username: user
Password: The password you chose during the install.

We hope you enjoy your new site. Thanks!

--The WordPress Team
http://ww.wp.xz.cn/

Somebody can tell me what’s going on?