[Not a ZC bug] "Contact Us" PHP mail error

Zen version is 1.3.8a
PHP version is 5.2.42
Email Transportation Method set to PHP

Order confirmation, welcome email, etc, all work fine, so there is nothing wrong with the selected transportation method in my setup.

When I try to use this transport method with the Contact Us form, however I get an Could not instantiate mail function error. It ONLY occurs in the contact form.

I note that this has been discussed elsewhere as an issue, but always assumed to be an issue with the host server. It cannot possibly be an issue with my server if all other mail sends without problem using PHP mail function.

I was able to work around it by changing to transport via smtpauth, but this does not change the issue with the contact form, which should also work perfectly well under PHP mail function, given that all other mail functions work.

Anna718:

I was able to work around it by changing to transport via smtpauth, but this does not change the issue with the contact form, which should also work perfectly well under PHP mail function, given that all other mail functions work.

The reason it works via smtpauth is that your smtpauth mailserver has you fully authenticated when you use that method, whereas the "PHP" method does not authenticate you. And, since your contact-us message is set up to spoof the sender's name, using the PHP method on your server is causing your messages to be rejected before they're even sent.

Thus, it's not a bug in Zen Cart. Instead, it's a security limitation of your hosting company's setup and/or your choice of email addresses.