To add to kris we will need more information on your hosting environment so we can determine if you even have a local mail server and if your ports are open for this. Some hosts even take it a step further to block certain mail ports.
There is a mailgun driver for mail built into Flarum, I think this would bypass your mail issues if your ports are blocked by your hosting provider, since it’s an API call. (I’ll have to take a look into this to confirm, but could close a gap for many… but price is another factor of course)
