By default Wordpress uses plain PHP mail which is not very reliable. It is better to use SMTP. I could sugges using a plugin like Easy WP SMTP. This would allow to easily integrate SMTP functionality to your site.
Then you could either setup an SMTP service on your droplet, to set that up you could follow the steps here:
Or you could use an external SMTP provider like Gmail. This would increase the delivery rate of your emails a lot.
If for any reason this is still not working, make sure to allow outgoing SMTP traffic:
sudo ufw allow 25
sudo ufw allow 465
sudo ufw allow 587
sudo ufw reload
If you are still not receiving your emails even after that, you could test your outgoing connectivity on port 25 with this command here:
telnet smtp.gmail.com 25
If you are getting connection timeout, even after allowing the traffic via your firewall, then you could contact DO support team who will be able to guide you through getting mail functionality enabled on your Droplet and account!
Hope that this helps!
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