When you send an email from the web, the recipient receives an email that might look something like this:

emailname.gmail.com@rapidfunnel.us when in fact the email address is: emailname@gmail.com

The reason it looks like this is because the mail providers often do a reverse lookup to determine whether the email that was sent from rapidfunnel.us came from a server that they expect to send rapidfunnel.us email.  

We send the emails on behalf of users. If we did not change the address,the email would look like it came from gmail.com, and with reverse lookup, the mail providers would check to see if we owned Google's email servers (we do not) and they can then use that information to determine that we might be sending SPAM. By configuring the address and adding rapidfunnel.us, it improves delivery rates.

When the propsect hits 'Reply', the reply goes directly to your actual address. 

Note: if the propsect tries to save the user's address from the main mail app, they might need to edit the address by removing the rapidfunnel.us.