Contact us form emails not being received

I had this problem crop up in the past couple of days on a site I've been developing. We're due to launch on Monday and I'm going crazy.

I have two addresses entered in the admin > configuration > email options > "Contact Us" dropdown. The contact form used to be able to send to both no problem. The addresses are entered in the format OwnerName [email protected], Webmaster [email protected]. I've tried deleting one address so there's only one in the dropdown to no avail. Both addresses receive email from other sources fine, and are administered in Google Apps. The contact form messages are not stuck in spam folders. I tried entering into the "Contact Us" dropdown another email I own on a totally different domain that's not administered by Google Apps, also to no avail.

I have email archiving turned on and the messages from the Contact Us form are showing up in the table in phpMyAdmin but they're not reaching their destination.

I checked the FAQ under problems sending/receiving email. I haven't changed anything in the store's email config recently, and order confirmation emails are going out fine to test customers with accounts so I'm guessing it's not a problem in the email config but rather in the contact form.

I can send email using admin > tools > send email.

I haven't updated ZC recently or done anything other than install (and then uninstall) Newsletter-Only Subscription. Oh, I also renamed the admin folder, but that hasn't caused any problems elsewhere.

At the same time as this I've had problems with order confirmation emails not getting sent to COWOA customers. I posted a message in the COWOA forum detailing that problem. Might they be related?

Thanks so much for any help you can give!

Store setup

ZC v1.3.9d
MySQL v5.1.52-cll
PHP v5.2.17

Modules added

CEON URI mapping 3.6.3
Column Layout Grid 1.3.8
Email Address Exporter 1.2c
EZ-Thumbnails v.1.01
EZ-Page Improved TOC 1.1
Giftwrap 2.8
HideCategories 2.0
IntegratedCOWOA 2.0c1
RECENTLY UNINSTALLED Newsletter Subscribe 2.2.2

Well! I got this sorted. I followed the instructions here to set up SMTP in the E-mail Configuration. I didn't try that first off because the contact form used to send without SMTP set up.

I decided to try this after entering a non-Google-Apps-hosted email address in the Contact Us dropdown and successfully sending a Contact Us form message to that address. The message arrived after a delay, but it got there. So I figured the simplest explanation must be the correct one, and the contact form couldn't send to a Google Apps-hosted email address, so I followed the troubleshooting tip. The knowledge shared in this forum and in the tutorials and wiki is so comprehensive and helpful! Thanks everyone!

So, when exactly did this problem suddenly start?

Do the emails show in the archive log, assuming you've turned that on for debugging? If they do show up in the log, then the problem is after Zen Cart hands the email off to the email servers, and not with Zen Cart itself.

http://www.zen-cart.com/wiki/index.php/Troubleshoot_-_Email_Problems
http://www.zen-cart.com/wiki/index.php/Troubleshoot_-_Understanding_Causes_Of_Lost_Emails

Oh ... yet another problem caused by google.

Heh, yes, they can cause some problems, but I've had better luck with Google Apps than with the email hosting provided by many web hosts, so I keep using them. Thanks for the links...hopefully this will help the next hapless Google Apps user....