Paypal IPN
You may find that your Paypal Standard transactions do not change the status of the order to ‘processing’ even though Paypal says that the payment has been received. This is usually down to the enabling of ‘Instant Payment Notification (IPN)’, which should be automatically enabled in your Magento Paypal settings. To check that they are correctly configured in your Paypal settings you need to login to your Paypal account and go here:
My Account > Profile > Instant Payment Notification preferences
Once inside, click on ‘Edit IPN Settings’ and you’ll be shown the form below:

You need to enter your Magento store name followed by the Paypal IPN directory structure. If you do not haveĀ URL rewrites enabled on the site, don’t forget to include /index.php before the Paypal folder, making it: http://www.storename.com/index.php/paypal/standard/ipn/
Then you need to enable it by selecting ‘Receive IPN messages’.
There’s a more comprehensive guide to enabling IPN on your Paypal Standard payments here: http://www.magentocommerce.com/wiki/how_to/paypal_standard_payments_setup_with_ipn

February 15th, 2010
Thanks for the help, Paypal don’t make it clear that you have to enable IPN.
June 27th, 2010
Hi,
I have enabled IPN but I also trade on Ebay. Paypal is trying to send IPN for them too and its failing whats solution for that.