In most cases they are getting the emails if one is getting them. Like @ryanpq said having more info is critical like domain. My guess and this is here for others searching similar things is that the mail is getting listed as spam. When you run your own server you need to do more with the mail settings then a host that provides mail servers and maintains them for you.
In most cases you don’t have DKIM set or the TXT records saying that mail from your domain, are sent from your server. For example a TXT record that says a server is allowed to send mail for the domain.
v=spf1 a mx ip4:45.XX.XXX.XXX ?all
All mail should be signed from the server using DKIM. “DomainKeys Identified Mail (DKIM) lets an organization take responsibility for a message that is in transit. DKIM provides a method for validating a domain name identity that is associated with a message through cryptographic authentication.”
If you have more information like domain, DNS you have set for mail, and server setup we can help you more.