The newsletter has its own custom settings under the newsletter builder menu, this example screenshot should show you where you need to look:

http://www.awesomescreenshot.com/image/562924/6f3a0212ea6fea5e910909f5aeac5e74

Cheers,

Greg

Nice to hear from you!

For the Email Settings(Admin > General Settings > Email Settings).

It seems not related the newsletter plugin.   I tried a Gmail account on Newsletter plugin "From Email".    It is different from cmsBuilder Email settings.

It also works.

Is it send via the "From Email" email server?

Hope you know what I mean.

Thanks!

Here are responses to your questions:

1. You shouldn't leave the field blank, as this will stop the CMS being able to send the emails, as a from email is required. 
2. You can set this email address to be whatever you want, but some email addresses are much more likely to get delivered to the user's inbox than spam box. For example I'd recommend using the same domain name as is used by the website. No-reply is good account name to use.
3. You should be able to find the newsletter sending settings under Newsletter Builder -> Settings in your main CMS Builder menu

Let me know if you have any other questions.

Thanks!

Greg

About the Newsletter "From Email" setting.

1) Can I leave the field blank?

2) If I want to set the From Email as no-reply@xxxx.com. This email does not exist.

would it cause error?

3) Where is the newsletter sending settings on cmsAdmin?

Thanks!

Jax