I'm building a home lab to prepare for Tier 1 or Tier 2 IT support work. I've practiced networking, ticketing systems, Microsoft 365 administration, Active Directory, and Group Policy, including a multi-branch lab with several departments.
I recently installed hMailServer on a Windows Server 2022 virtual machine and created two local accounts: [email protected] and [email protected]. I'm trying to send messages between them using Thunderbird from a separate Windows 11 virtual machine. hMailServer is configured with IMAP on port 143 and SMTP on port 25, but sending mail produces a connection error.
What should I check first, and is there another free mail-server application that would be better for a home lab?
4 Answers
Check the MX record or equivalent internal DNS entry for the lab domain, and confirm that the mail server’s hostname resolves to the correct VM address. After correcting the bindings, DNS, and firewall settings, internal messages began working in the lab. For practicing mail administration, hMailServer is fine; switching software probably won’t fix a basic connectivity or configuration issue.
Using a .local domain can be awkward because it is intended for local network naming and is not a publicly registered mail domain. It can still work for isolated internal testing if DNS is configured correctly, but make sure both virtual machines resolve the mail host and domain consistently. If you later try to send mail to the public internet, a self-hosted server may also have delivery and spam-reputation problems.
Start by testing from the hMailServer machine itself. Try sending and receiving locally, then verify that the workstation can reach the server on the required ports. You can test connectivity to SMTP on port 25 with Telnet or another network utility. If that works, review the Thunderbird server names, ports, and authentication settings.
Check the basics in hMailServer: DNS resolution, SMTP bindings, the configured domain, and whether the service is listening on port 25. Also verify that the Windows firewall or another network firewall is not blocking SMTP or IMAP. For a lab, allowing SMTP connections on port 25 is necessary, while the client’s source port will usually be selected automatically.
The firewall is worth checking, especially on the server VM. Make sure the hMailServer service is bound to the correct interface and that inbound rules allow ports 25 and 143.
The server is running on a Windows Server 2022 VM, and I’m using Thunderbird from a separate Windows 11 VM. I’ll test local delivery first, then check connectivity between the two machines.