SSL https Request open everybody the Windows certificate Messagebox (the certificate has saved)

Steps to reproduce:
1. Create a HTTPService to load a XML File from a https://xyz:443 (SSL) Server
2.
3.

Actual Results:

The Windows Messagebox for saving certificate comes everybody, wenn i call the httservice.send().
But the certificate is saved on the Client Windows PC.

Expected Results:

The window to store the certificates should be only uniquely indicated.
The certificate was already stored with first message.
I transfer many files by https:// protocoll and get everyone times this message

Workaround (if any):

None. I must click every time the Messagebox for new xml transfer over https://