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SMTPEmailRelay7 min read

Configure SMTP relay for sending emails

Configure an SMTP relay on Windows Server so your applications can send emails.

An SMTP relay allows your applications to send emails through an external mail server.

Step 1 — Install the IIS SMTP service

powershell
Install-WindowsFeature SMTP-Server -IncludeManagementTools

Step 2 — Configure the SMTP server

Open IIS 6 Manager:

powershell
# Open the SMTP management console
inetmgr6.exe

In the console:

  1. Expand the server > SMTP Virtual Server
  2. Right-click > Properties
  3. On the Access tab > Relay > add 127.0.0.1
  4. On Delivery > Smart Host > enter your external SMTP server

Step 3 — Configure relay with PowerShell

powershell
# Configure smart host (external relay)
$smtp = [ADSI]"IIS://localhost/SmtpSvc/1"
$smtp.SmartHost = "smtp.yourprovider.com"
$smtp.SmartHostType = 2
$smtp.SetInfo()

Step 4 — Use Send-MailMessage (simple method)

To send emails directly from PowerShell:

powershell
$params = @{
    From = "server@mydomain.com"
    To = "admin@mydomain.com"
    Subject = "Server Alert"
    Body = "The backup completed successfully."
    SmtpServer = "smtp.gmail.com"
    Port = 587
    UseSsl = $true
    Credential = (Get-Credential)
}
Send-MailMessage @params

Step 5 — Configure with hMailServer (alternative)

Download and install hMailServer for a complete SMTP server:

powershell
# After installing hMailServer
# Configure relay in the admin interface:
# Settings > Protocols > SMTP > Delivery of email
# Smart host: smtp.yourprovider.com
# Port: 587
# Authentication: provider username and password

Step 6 — Configure applications to use the relay

In your application, configure SMTP pointing to localhost:

terminal
SMTP Server: 127.0.0.1
Port: 25
Authentication: None (local relay)

Step 7 — Test sending

powershell
# Quick test with telnet
Test-NetConnection -ComputerName 127.0.0.1 -Port 25

# Send test email
Send-MailMessage -From "test@mydomain.com" -To "you@email.com" -Subject "Test" -Body "It works" -SmtpServer 127.0.0.1

Step 8 — Firewall

powershell
# Only allow SMTP from localhost
New-NetFirewallRule -DisplayName "SMTP Local" -Direction Inbound -Protocol TCP -LocalPort 25 -RemoteAddress 127.0.0.1 -Action Allow

With the SMTP relay configured, your applications on the Baires Host Windows VPS can send notifications and alerts via email.

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