I set up a domain on Google Apps with some email addresses, and wanted to send contact information from a WordPress form that was using Formidable. However, the emails weren’t being sent correctly from the form. When I sent a message from my Gmail account, the message went through correctly (I set up another email on the same domain for testing purposes).

Inspecting the mail error logs (for me on the shared hosting, was at ~/mail/new/*), I got things similar to the following:

Return-path: <>
Envelope-to: username@zzzzzzz.com
Delivery-date: Thu, 15 Dec 2011 15:19:24 -0700
Received: from mailnull by zzzzzzzz.com with local (Exim 4.69)
id 1RbJe8
for username@zzzzzzzzzz.com; Thu, 15 Dec 2011 15:19:24 -0700
X-Failed-Recipients: admin@mywebsite.com
Auto-Submitted: auto-replied
From: Mail Delivery System <Mailer-Daemon@zzzzzzz.com>
To: username@zzzzzzz.com
Subject: Mail delivery failed: returning message to sender
Message-Id: <E1RbJe8@zzzzz.com>
Date: Thu, 15 Dec 2011 15:19:24 -0700

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

  admin@mywebsite.com
    No Such User Here

I searched around a bit, and it seems like it was Google Apps rejecting the email that I was sending from the shared hosting environment. To solve this, I wanted to authenticate with Gmail and use that as the SMTP server.

I followed the instructions here and it seemed to work out well. I was able to send emails effectively to the Google Mail account after putting in my testing account’s information as the username/password. This worked with WordPress 3.1.

Hope this helps!