Suggestions for a Mail Server?

I’m thinking of moving away from the shared hosting of GoDaddy (I’m frequently getting the mails stating over using resources).

So I took a Digital Ocean droplet ($5 per month one) and configured everything else on it. However, one thing (mail server) is still preventing me from making a full switch.

Any recommendations on one?

I’m currently checking Dovecot, but not sure if it can be run with the same server.