Paypal IPN and PDT error

[joshlfisher]

When I fill in the link to the return URL for paypal IPN, Paypal gives me this error:
We were unable to validate the URL you have entered. Please check your entry and try again.

I know the link is good. What else should I check into?

[joshlfisher]

I really must have help on this. The paypal IPN feature is REQUIRED by my client. I have no idea what to do, if Paypal tells me the IPN URL cannot be validated.

[svgweb]

Hi, I am having this same problem.
When I imput the IPN URL paypal keeps giving me a message saying they cannot verify the URl.

Please Help.
Thanks

[Jason Caldwell]

Hey guys. Thanks for reporting this important issue.

Here are some things I would take a look at, as they are very common issues:

1. Do you have the IPN URL entered correctly?
Your PayPal IPN will look something like one of these:

Code: Select all

http://www.example.com/path/to/wordpress/?s2member_paypal_notify=1
http://www.example.com/?s2member_paypal_notify=1

2. Does your web host block external connections from unknown browsers? Whenever PayPal connects to your site, it's not the same thing as a normal web browser. PayPal's IPN service connects with an HTTP POST, which is sometimes blocked inadvertently by your host, resulting in the type of error that you're describing. I would contact your hosting provider and ask them to review the security restrictions configured on the firewall that guards your server. Please refer them to this article posted by PayPal.
( This lists all of PayPal's IP addresses. Can be used for whitelisting. )
https://cms.paypal.com/us/cgi-bin/?cmd= ... echecklist

Another issue that I've seen recently, is that a hosting company will "require" cookie authentication by all incoming visitors to your site ( including PayPal IPN connections ). This type of protection is designed by hosting companies to thwart DDoS attacks, by setting an validation cookie, followed by an initial redirection to weed out bots. Unfortunately, this method is also very good at causing problems with PayPal's IPN service. A hosting company can use the information provided here to re-configure your firewall to allow incoming connections from PayPal.

3. Do you have a maintenance mode plugin installed? If you've installed a plugin that has taken your site out of the public view, for the purpose of conducting tests during development; you'll need to remember that this will also affect connections requested by 3rd-party services like PayPal ( i.e. the verification process ), which would lead to an error such as you've described.