Nextcloud acquires webmail service Roundcube

Roundcube is webmail only. What you are referring to is self-hosting actual mail servers (for sending and receiving). And yes, that is a bit more difficult. Not because setting up a mail server is difficult, but a mail server must have a good “reputation”, otherwise mail goes straight to the spam folder or /dev/null (bounce is 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 the PTR record, SPF, DKIM, etc. These are all mechanisms to indicate to the receiving server that “you” are really allowed to send emails on behalf of that account. But then you still have a (major) risk that the server’s IP address is or will be on a blacklist. IP addresses of ISPs are normally already blacklisted anyway (+ that ISPs usually do not accept outgoing traffic to port 25 (and 587?) at all, or only allow this to the ISP’s mail server itself, which requires authentication and then serves as a relay) . And it is also difficult with VPSs, because a large IP block that includes the server’s IP can be blocked. You can usually have it unblocked, but you must first know that it is blocked at all.

I have been running a mail server for years, and it works fine. Never had any problems with incoming mail either. I don’t send outgoing emails very much. But do know that everything from Microsoft (both the consumer @outlook.com / @live.com / … and the business hosted Exchange solutions) deleted my mail straight away (/not received nor bounced, so the recipient really doesn’t receive anything, 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 much easier to use an SMTP relay. Such as MailChimp. SMTP2go, etc etc.. They do have a good (IP) reputation, so mail that goes through their servers will be accepted unless your domain name is actually blacklisted (or of course blocked on content). But of course SPF & DKIM etc. must also be configured correctly (they supply the DNS records that you have to set yourself).