I've recently upgraded / patched a Magento store to version 1.9.2 (from 1.9.1 via Magento Connect). It runs on a Centos server using PHP 5.5.26. Everything seems to work fine except I'm not getting any sales transaction emails from the store.
I've verified that php mail can send email from the server via a small php script invoked via browser. And this test used the same email from and to addresses used by sales transaction emails.
I can see in the exception log that the cron task is running, but it is generating an exception that ends with:
"exception 'Zend_Mail_Transport_Exception' with message 'Unable to send mail. ' in ...lib/Zend/Mail/Transport/Sendmail.php:137".
I've researched this error, but have not found anything leading to a solution.
I've verified the sales transaction emails are queued in the database (
core_email_queue table) just waiting for the cron task to initiate sending.
I've even tried setting up a free Mandrill account and installed the MageMonkey extension. But, that is not sending emails either.
Still looking for a solution. Any suggestions on where to look would be appreciated.