Setting up your own mail server on Windows is easier than many people think. If you’re looking for a free, open-source SMTP server solution for Windows, hMailServer is one of the best options available.

Requirements

• A registered domain name
• A Windows machine (Windows 10, Windows Server 2016/2019, or newer)
• Open port 25 on your server

Checking if Port 25 is Open

1. Go to Control Panel → Windows Features → enable Telnet Client.
2. Open Command Prompt and run:

   telnet smtp.gmail.com 25

   If you see a connection message, port 25 is open. Otherwise, it’s blocked.

Installing hMailServer

1. Download hMailServer from the official website.
2. Run the installer and set an administrator password. This password will be required to access hMailServer’s admin panel.

Configuring hMailServer

1. Adding Your Domain

1. Open hMailServer Administrator.
2. Go to Domains → Add.
3. Enter your domain name and click Save.

2. Adding Email Accounts

1. Go to Accounts → Add.
2. Enter a username (e.g., user@yourdomain.com) and password.
3. Click Save.

Generating and Adding a DKIM Key

To improve email deliverability, configure DKIM:

1. Download and install OpenSSL for Windows.
2. Open Command Prompt (as Administrator) and run:

   
   cd "C:\Program Files\OpenSSL-Win64\"
   openssl.exe genrsa -out dkim.private.key 1024
   openssl.exe rsa -in dkim.private.key -out dkim.public.key -pubout -outform PEM
                   

3. In hMailServer, go to Settings → Advanced → DKIM Signing.
4. Specify the selector (e.g., mail) and the path to dkim.private.key.

Configuring DNS Records

In your domain’s DNS settings, add the following records:

Type	Host	Value
A	mail	Your server’s public IP address
TXT	@	v=spf1 a mx ip4:YOUR.IP.ADDRESS ~all
TXT	_dmarc	v=DMARC1; p=quarantine; rua=mailto:dmarc@yourdomain.com; ruf=mailto:dmarc@yourdomain.com; sp=quarantine
TXT	mail._domainkey	v=DKIM1; k=rsa; p=YOUR_PUBLIC_KEY

Testing Your Email Server

Use a mail client such as Thunderbird or Outlook with these settings:

Host	localhost
User	user@yourdomain.com
Password	Your account password
Port	587
TLS	None

Conclusion

With hMailServer, setting up a fully functional Windows-based mail server is straightforward. By adding DKIM, SPF, and DMARC, you can significantly improve email deliverability and security.