special characters in URL

Hi, we are doing B2B HTTP:IDOC scenario. in this vendor provided a URL . but it contains special charatects like ? & . when we are going to add this URL in SM59 .we got error thats we changed " ?" as "%3F" and " &" as "%26". then URL saved . but when we try for test connection we got HTTP 404 error.

we send a test po for this then we got error msg like" Codepage conversion error Codepage Conversion from codepage DEFAULT to system codepage"

now the problem is

1. XI side or With URl

2. In XI Can we use URL with special characters? then is there any procedure to use?

3.In what way we can resolve this issue.