I recently upgraded my computer to macOS 10.13 and found that my iMessage (in
Messages.app) wasn’t working entirely and that Google Talk in the same app
would only receive messages and not send.
Starting with the Google Talk issue, that’s an easy one. Apple has removed
“official” support for Google Talk from Messages.app but they’ve clearly left
the code in place that allows your old account to login, connect and actually
receive messages, but helpfully added a dialog that says “Your message could
not be sent. Support for the targeted service Google Talk has …