I fucking hate web development and fuckton of issues it has. Laravel library not found despite the files exists and composer loaded it in the autoloader, fix: create a config file for the lib, why? Because magic. The code cannot find the provider class without it....
Next, try out smtp mail. Works everywhere, but not with the live smtp server. Fails with Invalid recipients error. 2 hours later, with half of my hair torn out I finally figured out. Can you guess?
Credentials and settings are correct, recipients are also correct. The fucking from address parameter was the culprit because you cannot send emails on behalf another address, logical but fuck that error message. Why is it that hard to respond with an understandable response?