Magento – Magento emails are not going

Found something from http://www.aschroder.com/2010/06/new-smtp-pro-magento-email-extension-released/ that might solve your issue.

Great extension, Ashley, thanks! Have been using it for about a year now without any issues.

For anyone on a VPS server suddenly getting “535 Incorrect authentication data” error, it is caused by the automatic WHM upgrade which changed one of the server email settings.

So, if you are on a VPS server using SMTP Pro and suddenly all outgoing emails stop working, here is one possible issue to check for:

1) Login to WHM
2) Under Server Configuration, select Tweak Settings
3) Click on the Mail tab
4) Scroll down to “Restrict outgoing SMTP to root, exim, and mailman (FKA SMTP Tweak)” and make sure it’s set to “OFF”
5) Scroll to the bottom of the page and click Save

Hope this helps someone with similar setup!
Peter

As of Magento 1.9.1.0 all Magento e-mails (including order confirmation and transactional) are now queued and sent according to your configured cron schedule.

From the release notes:

It's more important than ever for you to configure a Magento cron job. In addition to indexing and other core functions, all Magento e-mails (including order confirmation and transactional) are now queued and sent according to your configured cron schedule.

So I think you have to check configuration of Magento Cron Job. Here you can learn more about how to set them up.