SMTP email setup#

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In a production environment, Mattermost requires SMTP email enabled for email notifications and password resets when using email-based authentication.

Set up an SMTP email service#

Any SMTP email service can be used. You need a copy of the following information: Server Name, Port, SMTP Username, and SMTP Password.

Tip

If you don’t have an SMTP service you can set one up with Amazon Simple Email Service (SES):

  1. Go to Amazon SES console then SMTP Settings > Create My SMTP Credentials.

  2. Copy the Server Name, Port, SMTP Username, and SMTP Password values. You’ll need these values to configure Mattermost.

  3. From the Domains menu, set up and verify a new domain, then enable Generate DKIM Settings for the domain. We recommend you set up Sender Policy Framework (SPF) and/or Domain Keys Identified Mail (DKIM) for your email domain.

  4. Choose a sender address like mattermost@domain.com and select Send a Test Email to verify setup is working correctly.

Alternatively, you can use one of the services listed below, or can set up local sendmail by setting Server Name 127.0.0.1 with Port 25.

If deploying Mattermost using Docker, the standard docker 172.16.0.0/12 IP range isn’t used. Specify the IP range 192.168.0.0/24 to the email service to avoid relay access errors. If using postfix, under /etc/postfix/main.cf, specify mynetworks = 192.168.0.0/24. This may vary depending on how Mattermost is deployed. Ensure that Port 25 is open if a firewall is present.

Configure SMTP settings#

  1. In Mattermost go to System Console > Authentication > Email, and set Allow Sign Up With Email to true.

  2. In the System Console, go to Notifications > Email and configure Mattermost for your SMTP service. See the SMTP configuration documentation for details.

  • Set Send Email Notifications to true.

  • Set the Notification Display Name for the account sending notifications.

  • Set Notification Email Address for the email address used to send notifications.

  • Enter the SMTP Username, SMTP Password, SMTP Server, and SMTP Port you copied from initial setup.

  • We recommend setting Connection Security: to TLS (Recommended) to encrypt communication between Mattermost and your SMTP service.

  1. Select Save.

  2. Under Connection Security, select Test Connection. Mattermost will confirm whether a connection to the SMTP service is successful by sending you an email. If the test fails, Mattermost will provide details about why it failed in the System Console. See the check Mattermost logs section below for details.

Sample SMTP settings#

  • Set SMTP Username to [YOUR_SMTP_USERNAME]

  • Set SMTP Password to [YOUR_SMTP_PASSWORD]

  • Set SMTP Server to email-smtp.us-east-1.amazonaws.com

  • Set SMTP Port to 465

  • Set Connection Security to TLS

Make sure Postfix is installed on the same machine as Mattermost.

  • Set SMTP Username to (empty)

  • Set SMTP Password to (empty)

  • Set SMTP Server to localhost

  • Set SMTP Port to 25

  • Set Connection Security to (empty)

  • Set SMTP Username to your_email@gmail.com

  • Set SMTP Password to your_password

  • Set SMTP Server to smtp.gmail.com

  • Set SMTP Port to 587

  • Set Connection Security to STARTTLS

Warning

Additional configuration is required in Google to allow SMTP email to relay through their servers. See SMTP relay: Route outgoing non-Gmail messages through Google for the required steps.

  • Set SMTP Username to your_email@hotmail.com

  • Set SMTP Password to your_password

  • Set SMTP Server to smtp-mail.outlook.com

  • Set SMTP Port to 587

  • Set Connection Security to STARTTLS

  • Set SMTP Username to your_email@hotmail.com

  • Set SMTP Password to your_password

  • Set SMTP Server Name to smtp.office365.com

  • Set SMTP Port to 587

  • Set Connection Security to STARTTLS

Troubleshooting SMTP#

TLS/STARTTLS requirements#

If you fill in SMTP Username and SMTP Password then you must set Connection Security to TLS or to STARTTLS

Troubleshooting using logs#

If you have issues with your SMTP install, from your Mattermost team site go to System Console > Logs to look for error messages related to your setup. You can do a search for the error code to narrow down the issue. Sometimes ISPs require nuanced setups for SMTP and error codes can hint at how to make the proper adjustments.

For example, if System Console > Logs displays the following error, search for 554 5.7.1 error and Client host rejected: Access denied.

Connection unsuccessful: Failed to add to email address - 554 5.7.1 <unknown[IP-ADDRESS]>: Client host rejected: Access denied

Checking your SMTP server is reachable#

  • Attempt to Telnet to the email service to make sure the server is reachable. For additional information, visit https://docs.microsoft.com/en-us/exchange/mail-flow/test-smtp-with-telnet?view=exchserver-2019. If you’re using an earlier version than Exchange Server 2019, select your version from the left-hand navigation menu.

  • You must run the following commands from the same machine or virtual instance where mattermost/bin/mattermost is located.

  • Telnet to the email server with telnet mail.example.com 25. If the command works you should see something like:

    Trying 24.121.12.143...
    Connected to mail.example.com.
    220 mail.example.com NO UCE ESMTP
    

    Then type something like HELO <your mail server domain>. If the command works you should see something like:

    250-mail.example.com NO UCE
    250-STARTTLS
    250-PIPELINING
    250 8BITMIME
    

Note