How to Stop Email Spam by Multisite

Hi,

I wanted to do two things to the sign up process.

1. All Emails should "NOT" Land in Spam folder.

Currently the welcome mail,activation mail and further automessage mail almost everything from my site lands in Spam folder.

I tried your ultimate Branding Email From option and set it as "no-reply@mysitte.com.

I have one Email Id hosted with Google Apps and MX records are changed to Google.
But on the welcome mail, it shows mailed by "gator4188.hostgator.com" This is making the Email to Land in Spam.

Please help me to deliver the Emails in Primary mail box.

2. How do I customize the Welcome mail and Automessage Design (Currently it is plain Mail without any design)