If you are receiving error messages when forwarding emails to Mailparser, or your emails are not arriving after setting up automatic forwarding from Office 365 this may be caused by the Security Change Microsoft Implemented on October 5, 2020, which by default blocks forwarding to external recipients.
To correct the issue, go to https://protection.office.com and navigate to Threat Management > Policy > Anti-Spam Policy > Outbound spam filter policy. Then select EDIT POLICY.
Under the Outbound spam filter policy Edit screen, select “On- Forwarding is enabled” under the Automatic Forwarding section. Click SAVE.
Once this is completed your emails should arrive in Mailparser correctly. For more information consult the Microsoft documentation here: https://docs.microsoft.com/en-us/microsoft-365/security/office-365-security/configure-the-outbound-spam-policy?view=o365-worldwide