This answer on SO appears to be what you're looking for. There are conflicting answers on the post, but it appears that if you set the URL for your IPN listener at the code level i.e. in your PayPal form you defined notify_url
, then there is no way of updating this.
From the top answer on the aforementioned post:
I had exactly the same problem .... I had to move servers which meant my IPN url changed. I have spoken to 3 different paypal reps and even had a meeting with a tech support guy from there.
Unfortunately, there is NO WAY to change the IPN url for existing customers/subscriptions.
I have been advised that all existing customers/subscriptions would need to be setup again, your customers would then need to start a new subscription based on the new IPN url. This is a right PITA ... I have just over 1500 customers I need to do this for, and I can guarantee I will lose some due to the hassle of this.
Sorry this wasn't the answer you were looking for :(
If it's viable, I would leave the IPN listener where it is.
However, the answer above is a few years old and there might be a solution I'm not aware of. Perhaps you could contact customer support.