'Message delivery submission failed 120 / HTTP 422 (Microsoft)'
120 MailSubmissionFailed The server failed to submit the message for delivery.
This delivery error from Microsoft is specific to users with a linked Outlook mailbox. Messages sent from Apollo are sent through the Nylas API (more information here) so if we return this error on any of your messages, confirm the following recommended by Nylas' support doc:
1. Your send-from email address is the same as the address synced
For example, if you've connected the account
firstname.lastname@example.org, but you set the from email as
email@example.com sending through the Nylas API, you might receive 120 / 422 error from Microsoft. You might see an exception like
Exception message: MapiExceptionSendAsDenied: Unable to submit message. in your Exchange logs.
2. Your Exchange server has not quarantined the syncing devices Nylas uses to sync
3. Your email account settings follow Nylas' Suggested Office 365 Settings
Whitelist Nylas' IP Addresses
If you can confirm the above, it's possible your mail server has blocked Nylas from sending messages on your behalf. If your email account settings have a whitelist security feature, you'd need to whitelist Nylas' IPs.
We recommend reaching out to your email admin to confirm and then, based on this Nylas resource, whitelist all IP ranges designated "us-west-2" in the JSON file provided here: http://docs.aws.amazon.com/general/latest/gr/aws-ip-ranges.html
Important Note: These instructions do not apply if you're using Sendgrid. Refer to #5 in our Sendgrid documentation.