SSMTP is a program to deliver an email from a local computer to a configured mailhost (mailhub). It is not a mail server (like feature-rich mail server) But it is using sendmail and does not receive mail, expand aliases or manage a queue. One of its primary uses is for forwarding automated email (like system alerts) off your machine and to an external email address.

With SSMTP on Openwrt you can use command or text email’s draft to send email from OpenWrt


Minimum free space requirements = (1.99 MB)

Installation and Configuration

Step 1: Install SSMTP

  1. Open OpenWrt’s LuCI Web’s Interface
  2. Select Tabs System – Software
  3. Click Update List
  4. In download and install packages type “ssmtp” then click ok

Step 2: Configure SSMTP

  1. cd /etc/ssmtp
  2. vi ssmtp.conf

Edit ssmtp.conf

Append following modified sSMTP configuration (below, it configured for Gmail  provider):


To test if SSMTP is working properly:

Using email draft

Create test email.txt on /tmp folder

Edit test email.txt using the proper formatting of SSMTP

Send email to destination.address using test mail.txt email’s draft


If SSMTP doesn’t work properly or can’t send email, you can try uncomment debug from ssmtp.conf then retry send email. you’ll get debugging information when sending email:

If you receive an unauthorized or “cannot open” while sending email, it is probably blocked by the email server due to the security authentication issue. Try to allow or disable security feature at your email provider (e.g. SMTP or POP3 configuration) or at Gmail you have to toggle “Allow less secure apps” to off.



  1. SSMTP – ArchWiki
  2. Image by Alec Perkins / CC BY 2.0