Check out: WordPress email notifications

But it was working before restarting the droplet so I don't think I need this

SSH into your droplet and run the following command:

echo test | mail your@emailaddress.com

Do you get the email address? What's the output of said command?

Apparently I had to install postfix, but now it's not sending emails & when I try to run postfix I get this error

`postfix/postfix-script: fatal: the Postfix mail system is not running`

when I `tail` `mail.err` & `mail.log` I see these errors

Sep 13 11:24:43 localhost postfix/postfix-script[18026]: fatal: the Postfix mail system is not running
Sep 13 11:24:54 localhost postfix/master[18130]: fatal: bind 0.0.0.0 port 25: Address already in use
Sep 13 11:25:01 localhost postfix/postfix-script[18148]: fatal: the Postfix mail system is not running
Sep 13 11:25:04 localhost postfix/master[18249]: fatal: bind 0.0.0.0 port 25: Address already in use

Do you need to send mail from your droplet for anything else, other than WordPress?

Try restarting your droplet. That should fix it.

Having the same issue, terminal said
/usr/lib/sendmail: No such file or directory

after

echo test | mail your@emailaddress.com

I am going to do some more digging to find the fix.

May not be related to this post, but I did find the fix for my issue. I am running an Ubuntu droplet and it appears that I did not have an SMTP service setup.

Running apt-get install sendmail fixed my issue.

Original article here.
https://www.digitalocean.com/community/questions/php-mail-function-enable