PayPal Requested and configured merchant emails do not match
Magento is periodically logging the following error.
2015-07-12T13:52:18+00:00 ERR (3): exception 'Exception' with message 'Requested and configured firstname.lastname@example.org merchant emails do not match.' in /home/user/public_html/app/code/core/Mage/Paypal/Model/Ipn.php:257
In this error, the "Requested" email address is blank.
I verified that Magento has email@example.com under System --> Configuration --> Sales --> Payment Methods --> PayPal Payments Pro (Includes Express Checkout) --> Required PayPal Settings --> Payments Pro and Express Checkout --> Email Associated with PayPal Merchant Account, both in the Default Config and in the Main Website.
My guess is that the "Requested merchant email" and "Configured merchant email" correspond to the "Magento settings" and "PayPal.com settings" respectively. Is that correct?
Per the following thread, I tried manually deleting the contents of the cache directory, but that did not help.