Title: Authentication with Office 365 API problem
Last modified: September 10, 2026

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# Authentication with Office 365 API problem

 *  Resolved [tenerifeit](https://wordpress.org/support/users/tenerifeit/)
 * (@tenerifeit)
 * [3 weeks, 2 days ago](https://wordpress.org/support/topic/authentication-with-office-365-api-problem/)
 * Hi there,
 * I had the connection between Post SMTP and Microsoft365 API working perfectly
   fine and then all of a sudden all email sending is failing. 
   I did get this error
   message:Code: 401, Message: Unauthorized, Body: {“error”:{“code”:”InvalidAuthenticationToken”,”
   message”:”ArgumentNull”,”innerError”:{“date”:”2026-09-10T12:09:56″,”request-id”:”
   2e5a93b5-3341-4d0c-b6cf-15155931b040″,”client-request-id”:”2e5a93b5-3341-4d0c-
   b6cf-15155931b040″}}}
 * So, I have created multiple times now a new app in azure and double checked that
   all is created according to the step by step guide of post smtp, but I always
   do get the same error code. 
   Now even when I want ro rerun the configuration 
   wizard, I get this error:Error retrieving access token. Try Again Now.I have 
   wordfence installed, but I did try to run the firewall in learning mode, disable
   the firewall and even deactivate wordfence completely, but still the same problem.
 * Does anyone have an idea how I can fix this problem?

Viewing 1 replies (of 1 total)

 *  Plugin Support [mubashirbutt](https://wordpress.org/support/users/mubashirbutt/)
 * (@mubashirbutt)
 * [3 weeks, 1 day ago](https://wordpress.org/support/topic/authentication-with-office-365-api-problem/#post-19017176)
 * Hello [@tenerifeit](https://wordpress.org/support/users/tenerifeit/) ,
 * Please open a support ticket using the link below and use the **same subject 
   and details** as your current request. This will help our team review the issue
   with all the relevant information.
 * [Open a Support Ticket](https://objectsws.atlassian.net/servicedesk/customer/portal/16)

Viewing 1 replies (of 1 total)

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 * 2 replies
 * 2 participants
 * Last reply from: [mubashirbutt](https://wordpress.org/support/users/mubashirbutt/)
 * Last activity: [3 weeks, 1 day ago](https://wordpress.org/support/topic/authentication-with-office-365-api-problem/#post-19017176)
 * Status: resolved