Apache proxy throws error connecting to a third party
Solution 1:
Adding AllowCONNECT for the proxy port worked. That wasn't needed for Apache 2.2 but is for Apache 2.4. For us, it's from IBM HTTP Server 8.5.5 to IBM HTTP Server 9.
Prior comment has my virtual upvote since that doesn't work yet. You'd think they might take reputation points from Stack Overflow. Took a bit of searching to find this answer, so thanks.