One of the most common needs when setting up a new web server is sending email. The safest and easiest way to do this is to connect your server to a mailing service such as SendGrid or Amazon SES. Using an external service will help you avoid pitfalls like your server IP getting blacklisted by anti-spam services.
I’ve written a full tutorial over at DigitalOcean covering exactly how you set this up on your FreeBSD droplet.