Roundcube is webmail only. What you are referring to are actual self-hosted mail servers (for sending and receiving). And yes, this is a little trickier. Not that setting up a mail server is difficult, but the mail server must have a good “reputation”, otherwise the mail will go straight to the spam folder or /dev/null (bounces are actually rare). Receiving mail on your own server is much less of a problem.

If you want to use your own server, you will have to arrange all the basic things yourself. Such as PTR record, SPF, DKIM, etc. These are all mechanisms to signal to the receiving server that “you” are indeed allowed to send emails on behalf of this account. But then you still have a (significant) risk that the server’s IP address is or will be blacklisted. ISPs’ IP addresses are usually already blacklisted anyway (+ ISPs usually don’t accept outgoing traffic to port 25 (and 587?) at all, or only allow it to the ISP’s mail server itself , which requires authentication and thus acts as a relay). It is also difficult with a VPS, because a large IP block that includes the server’s IP address can be blocked. You can usually unblock it, but you should first know that it’s blocked at all.

I’ve been running a mail server for years, and it works fine. I didn’t have any issues with my inbox either. I don’t send outgoing emails very often. But know that everything from Microsoft (both consumer @outlook.com / @live.com / … and company-hosted Exchange solutions) immediately deleted my mail (/it was not received or bounced, so the recipient doesn’t really do it) I receive nothing, and I don’t know that the email was not “sent” (/received)).

If you really want to be able to send emails anywhere without any problems, it is easier to use an SMTP relay. Like MailChimp. SMTP2go, etc.. They have a good reputation (IP), so mail that passes through their servers will be accepted unless your domain name is already blacklisted (or of course blocked for content). But of course SPF, DKIM, etc. must also be configured properly (they provide DNS records that you have to set yourself).