How do I troubleshoot "Failed 120/HTTP 422" errors?

Article author
Eric Zrinsky


There are several reasons why you may receive sending errors within your Email Service Provider (ESP). For Microsoft Outlook, one of the more common and frustrating errors is Message delivery submission failed 120 / HTTP 422 (Microsoft). There are a few different tactics that you can use to diagnose and troubleshoot this error.

Refer to the sections below for information about how to troubleshoot this error.

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Troubleshoot "Message delivery submission failed 120 / HTTP 422 (Microsoft)" Errors

This delivery error is specific to users with a linked Microsoft Outlook mailbox.

Microsoft Exchange rejected your message. Message delivery submission failed 120 / HTTP 422 (Microsoft)


Messages sent from Apollo are routed through the Nylas Application Programming Interface (API). If you receive this error for any of your sent messages, confirm the following:

  • Is your send-from email address the same as the address synced within Apollo?
    • For example, if you've connected the account, but you set the from email as new_user@email.comwhen sending through the Nylas API, you might receive the 120 / 422 error from Microsoft. You may also see an exception like Exception message: MapiExceptionSendAsDenied: Unable to submit message. in your Exchange logs.
  • Has your Microsoft Exchange server quarantined the syncing devices Nylas uses to sync?
    • Check to see whether Outlook has any of the following potential issues:
      • The Mobile —> Mobile Device Access menu lists no quarantined devices.
      • You've enabled mobile device provisioning.
      • There are no conflicting device access rules as defined by the Suggested Office 365 Settings on the Nylas Docs site.

If you have additional questions about troubleshooting this error, refer to the Message Delivery Submission Failed article on the Nylas Knowledge Base.

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Whitelist Nylas IP Addresses

If your settings in Outlook all match the expected settings listed above, it's possible that your mail server has blocked Nylas from sending messages on your behalf. If your email account settings have a whitelist security feature, you should add the Nylas IP addresses to your whitelist.

Apollo recommends that you reach out to your company's email administrator to confirm whether you can add IPs to a whitelist. Then, refer to the instructions on the AWS Public IP Address Ranges Now Available in JSON Form. You should whitelist all IP ranges designated as "us-west-2" in the JSON file. This file is available on the Amazon AWS site of IPs.

Not Applicable To SendGrid Users

Please note, if you're using SendGrid with Apollo, the information above does not apply. Please refer to the Set Up, Configure, and Troubleshoot Your SendGrid Account article for more information about how to troubleshoot with SendGrid.

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