Configuring Outbound SMTP Authentication for On-Premise Devices and Application Servers

Document created by user.oxriBaJeN4 Employee on Dec 6, 2018Last modified by user.oxriBaJeN4 Employee on Jul 1, 2019
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Email can be sent and received from any device or application that supports POP and SMTP protocols. This guide outlines how to configure on-premise devices and application servers that need to send (but not receive) outbound mail. For example, application servers that need to send out alerts, and multi-function machines that need to send out scanned documents.




Consider the following:

  • If the email client has been configured to use encryption, but the encryption negotiation fails, Mimecast will not accept the connection.
  • The Mimecast internal domain user must have the POP and SMTP options enabled before email can be sent and received using these protocols.
  • New messages can only be sent outbound via SMTP authentication when using a Mimecast cloud password.
  • 2 factor authentication must be disabled for users to submit email using SMTP authentication. 


Configuring SMTP Authentication


To configure an SMTP authentication, you must create a specific user account for sending mail (e.g.<>):

  1. Log on to the Administration Console.
  2. Click on the Administration menu item. A menu drop down is displayed.
  3. Click on the Directories | Internal Directories menu item. A list of your domains is displayed.
  4. Click on a Domain. A list of the domain's users is displayed.
  5. Click on the New Address button.
  6. Fill out the dialog as below:
    • Enter the Email Address of the assigned administrator account.
    • Enter a Password for the account and make note of it.
    • Enable the Password Never Expires setting.
    • Enable the Allow SMTP Email Submission setting.
  7. Click on the Save button.
Cloud passwords, not domain passwords, must be used to allow SMTP / POP submission. Ensure the default application setting has cloud password enabled. See the Managing User Email Addresses page for further information.

Configuring the Device for SMTP 


Configure the device to:

  1. Use Mimecast's IP addresses as the SMTP server. See the table below for the IP addresses for your region.
  2. Use port 587.
  3. Enable authentication. Use the same login credentials (email address and password) as configured above.

Mail Server Description

Example Entry

The outbound mail server which emails should be sent through. It's important to enable TLS Encryption and to use port 587.Europe


North America

South Africa




Bypassing an Anti-Spoofing Policy


In specific customer accounts, an Anti-Spoofing Policy may be enabled to prevent unauthorized access to your Mimecast mail service. This is evident if during testing, an "550 Anti-Spoofing policy - Inbound not allowed" error is returned. In this instance, enable a bypass policy for your email address(es) in the Administration Console.


See Also...