over on gnupg-users, MFPA writes:
The broken link is at https://gnupg.org/software/swlist.html#sec-1-23. The link that returns the 403 error is http://sites.inka.de/tesla/gpgrelay.html. A possible working link is https://sourceforge.net/projects/gpgrelay/.
"Miranda ICQ [Unix] CHAT" also doesn't work. Maybe it would be a good idea to check all of them via script or something like that...
I fixed the gpgrelay link.
For Miranda the domain was changed in June, this may or may not be an indication that the project has been canceled. I leave it as it is, so people can use archive.org to lookup the old content. I don't think that automatic URL checkers make much sense here.