Some hosts have very specific requirements which can effect significantly the To & From Email Addresses you can use with CF7.
For example the from and to, on a DreamHost server, have to be the same domain as what you’re hosted on – see http://www.dreamhoststatus.com/2012/04/04/improvements-to-outgoing-spam-prevention-policy/.
See Contact Form 7 Email Issues. Most people that work through this information appear to be able to resolve their email sending & receiving issues.
You are correct, Dreamhost does have spam preventative measures that require your email script From headers to be either a dreamhost hosted email account or use smtp authentication to send your messages, as described below:
You could try to install & configure this WordPress plugin to use these
SMTP authentication settings:
http://wordpress.org/extend/plugins/configure-smtp/
If you install and use this plugin, this should correct all the
webforms/plugins on this site to use the settings you configured. Also make sure your wordpress username is tied to a dreamhost hosted email account.
Sample Plugin SMTP authenticated settings:
smtp server: smtp.gmail.com
ssl is on
smtp authentication is on
port 465
user: your.email@gmail.com
pass: your password
