SMTP email setup - Mattermost

import Tabs from '@theme/Tabs'; import TabItem from '@theme/TabItem';

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):

Go to Amazon SES console then SMTP Settings > Create My SMTP Credentials.
Copy the Server Name, Port, SMTP Username, and SMTP Password values. You'll need these values to configure Mattermost.
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.
Choose a sender address like [email protected] 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.

</Tip> <Note>

Outlook365 no longer supports Basic Auth which is required by Mattermost. We recommend using an alternate Email service like AWS SES (Simple Email Service).

</Note>

Configure SMTP settings

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

<Note>

SMTPPort and related port settings use string format (e.g., "465") for compatibility with the host:port binding format, which requires string concatenation.

</Note>

Select Save.
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

</TabItem> <TabItem value="postfix" label="Postfix">

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)

</TabItem> <TabItem value="gmail" label="Gmail">

Set SMTP Username to [email protected]
Set SMTP Password to your_password
Set SMTP Server to smtp.gmail.com
Set SMTP Port to 587
Set Connection Security to STARTTLS

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.

</Warning> </TabItem> <TabItem value="hotmail" label="Hotmail">

Set SMTP Username to [email protected]
Set SMTP Password to your_password
Set SMTP Server to smtp-mail.outlook.com
Set SMTP Port to 587
Set Connection Security to STARTTLS

</TabItem> <TabItem value="office365-outlook" label="Office365/Outlook">

Set SMTP Username to [email protected]
Set SMTP Password to your_password
Set SMTP Server Name to smtp.office365.com
Set SMTP Port to 587
Set Connection Security to STARTTLS

</TabItem> </Tabs>

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.

text

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

Checking your Notifications settings

If an SMTP connection test in the System Console for a self-hosted Mattermost deployment fails with the message Connection unsuccessful: Failed to set the to address: 550 5.7.27 [[email protected]](mailto:[email protected]), go to System Console > Site Configuration > Notifications to verify that notification settings are configured correctly, including Notification Display Name, Notification From Address, Support Email Address, and Notification Reply-To Address. Cloud administrators can't manage Notification From Address or Notification Reply-To Address.

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://learn.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:
text
```
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:
text
```
250-mail.example.com NO UCE
250-STARTTLS
250-PIPELINING
250 8BITMIME
```

<Note>

Telnet isn't included in official Mattermost Docker images, so you either need to use ping on those, or install Telnet yourself either directly or by modifying the Dockerfile.
For further assistance, review the Troubleshooting forum for previously reported errors, or join the Mattermost user community for troubleshooting help.

</Note>