Enabling SMTP Settings for an Outlook Inbox

If you are setting up SMTP overrides for an Outlook inbox, be sure to check the following information to ensure that everything is set up correctly.

Configuring Custom SMTP Settings for Outlook

  1. In your Accredible dashboard, click on 'Emails' at the top of your Accredible dashboard.
  2. In the left-hand sidebar menu, click on 'SMTP Overrides.'
  3. Enter the sign-in credentials of the hosted mailbox being used into the "username" and "password" fields.
  4. The fields in this section will need to be filled out as followed:

    Outgoing Server
    - smtp.office365.com

    Port - 587

    Encryption - TLS

    Authentication - Base64 encoded

  5. Save your changes. We recommend sending yourself a test email to confirm that Accredible is sending your emails from your inbox. You can do this using the 'Send Test Email' function on the SMTP Overrides page in Accredible.

Please note that if you change your Outlook account's password at any point, you will need to update the relevant field in Accredible. Failure to do so could result in emails not being sent to your recipients. 

Enabling SMTP AUTH for Outlook Mailboxes

We strongly suggest enabling SMTP AUTH in your Exchange Online organization if you have set up SMTP settings on your Accredible account and are receiving authentication errors. This is necessary for basic authentication with Accredible.

Please follow this guide on how to enable SMTP AUTH for Exchange Online: https://learn.microsoft.com/en-us/exchange/clients-and-mobile-in-exchange-online/authenticated-client-smtp-submission#enable-smtp-auth-for-specific-mailboxes

Multi-Factor Authentication and Microsoft Security Defaults

This option is incompatible with Microsoft Security Defaults or multi-factor authentication (MFA). If your environment uses Microsoft Security Defaults or MFA,  you cannot enable SMTP Overrides successfully.

For more information on how to set up a multifunction device or application to send email using Microsoft 365 or Office 365, here is Microsoft's Support article on this topic: How to set up a multifunction device or application to send email using Microsoft 365 or Office 365

Important Notes

  • You should avoid using Port 25 if that is an option for your SMTP configuration.
  • DKIM or SPF settings you previously configured with Accredible will no longer affect delivery since emails will be sent from your server instead of Accredible's.
  • If you update the login credentials for your email inbox you will need to update these in your SMTP Overrides setting within Accredible. Please do so to ensure your emails are sent successfully.


  • In order to keep systems healthy and safe, email hosts often limit the number of emails that can be sent in a 24-hour period.
  • This means that if you enable SMTP Overrides and issue a large batch of credentials (for example, 10,000), you run the risk of the request timing out and your emails failing to send.
  • We recommend checking the number of emails your server allows and issuing credentials in batches to remain under this limit. 


Has this article helped you? Let us know!

If you want to tell us about any improvements you feel could be made to this page, you can email us at support@accredible.com.