There is a limit for HTTP calls
https://support.microsoft.com/en-us/help/208427/maximum-url-length-is-2-083-characters-in-internet-explorer
Even if there was no limit, I would not recommend doing this. Depending on the capacity of the server, you could cause problems with the infrastructure of this server.
Could you explain your scenario better?
As I understand it you need to send 250k of content to some website, will you have that amount of items recurrently?
Do you have access to the database of this Site?