jjwinter
You can easily run a real mail server using a dynamic connection and a free domain.
My client has no domain name. The server is server.local The email they check is through their ISP.
Get yourself a free domain from dyndns eg yourcompany.dnsalias.com or whichever you prefer/choose.
Run "Configure this server" and change to this domain name instead of server.local as the main domain name. Also configure your dyndns account details so SME server will keep the dyndns account updated with your new external IP each time it changes.
I run into reverse DNS trouble when I try to send because the internal addresses are not real email addresses. I want to send using their external addresses.
In Server manager Email panel set the outgoing smtp server to be your ISPs smtp server eg mail.yourISP.com
Reconfigure your email clients to use the real external email address.
Alternatively you can disable the smtp proxy in server manager panel, and your email clients will send directly to your ISP. In that case use the SME server mail server for incoming but use your ISPs mail server for outgoing.
As a bonus you can test sending and receiving email using the new dyndns address and eventually convince the boss to use a real domain and a full mail server.