I’m one of the maintainers of BambooSMTP. I’m sorry to hear that you encounter some issue with our library.
We will investigate on our side to see if the issue is related to our latest releases. In the meantime, can you try the following?
Bump to the latest version of BambooSMTP, which is 4.0.0.
Don’t use the extra_applications key in mix.exs to load applications from dependencies. Elixir can do it by itself based on the return value of deps/0. Trying to load everything manually this way can lead to strange behaviour. Our README is misleading regarding that, sorry.
I will try these suggestions later today. Just wanted to say that I can reproduce the issue just by bumping bamboo from 1.6.0 from 1.7.0. I suspect it has something to do with Bamboo.Test.
I don’t think bamboo_smtp is the crux of the problem. It just forced an upgrade to Bamboo which seems to be the real cause of the issue. I’m not saying Bamboo is wrong or broken, we’re just probably using it the wrong way. I will RTFM later today to see if we’re doing something different from their testing docs.