Remove/ replace email header

How i can remove or sustitute the email header?
Now when a new user register on my site ajax send a notification with this sender: “mysite”@<wordpress@”mysite”>

I would like remove wordpress and put my personal information. Where can y take that?

Another question: Where i can translate the message that shows ajax when a new user register for first time? Now is in english and i would take a spanish message.

I hope anyone understand my english and can help me.

Thanks and regards,

http://wordpress.org/plugins/login-with-ajax/