This issue is rather odd. I have a Macbook Pro as a work computer. I have Choosy set up as the default browser and it is configured so all applications use Microsoft Edge. I have a single rule set up in Choosy so personal apps use my personal browser, Opera. Everything works as expected. A few months back I switched my personal email client away from Apple's mail client to eM Client (https://www.emclient.com). For some reason Choosy seems to be having problems with this email program. Sometimes it opens links I click in eM correctly (Opera), other times it doesn't work and it opens links in Edge. If I switch back to Apple's mail program, everything works perfectly again. I'm not sure why but Choosy appears to have issues with links in eM client that unfortunately seem random, no rhyme or reason as to why sometimes it fails and uses Edge.