I'll try to explain this as succinctly as possible. We have a Dockerized Laravel app up on Azure which is working fine apart from emails (Office365 smtp on port 587). We have two App Services...one for development and one for production. The only difference I can see between the two is that the production service has a Custom Domain attached.
Emails work fine from the development service but fail silently from the production one. Double checked the credentials, no difference. App logs show nothing and the app doesn't register any errors.
I have no clue what else I can investigate. I opened up port 587 using an outbound rule but that changed nothing. Any morsels of help are hugely appreciated.