I have an internet connection with a public, static IPv4 address (the IP address has a PTR record for foo.org domain, and I own foo.org domain, and have nameservers for it elsewhere, mx record is set to use the static ip). I have an OpenBSD i386 installed on a machine that is the only thing that uses this internet connection.

If I nmap all the port of it from the internet side, I can't see any open ports. Great. Since no service is running on the OpenBSD machine that is faced to the internet.

I need to install a mail server on it, so people could use it for sending/receiving e-mails securely.

So I googled and I will choose to install:

OpenSMPTd for SMTPS (using port 465)
popa3d for POP3S (using port 995)

Question: is this enough for a mail server? Will I be able to send/receive e-mails? (only port 465 will be open for the world/internet, pop3s will be only allowed from localhost, because we will use an ssh tunnel /with port knock/ to this openbsd machine to receive mail), so nmaping all the ports of the openbsd machine only outputs that port 465 is open.

UPDATE: so it turn out I don't really need a pop3 server, because I just need to log in to the openbsd machine, and there I can see the mails locally(afaik thunderbird can be set to see local mails.).