Forum Discussion

Brad Hawkins's avatar
Brad Hawkins
Copper Contributor
Feb 14, 2018

Bad Outbound Sender Issue

Hi Team, 

We're having an issue with a user who's account was comprimised and used to send spam. We've reset password and resolved the spam issue but now the user cannot send genuine emails with the below error: 

 

Generating server: TY1PR0301MB1216.apcprd03.prod.outlook.com

Remote Server returned '5505.1.8 Access denied, bad outbound sender AS(4201708241)'

Original message headers:

Received: from TY1PR0301MB1216.apcprd03.prod.outlook.com ([10.164.98.14]) by

TY1PR0301MB1216.apcprd03.prod.outlook.com ([10.164.98.14]) with mapi id

15.20.0506.020; Thu, 15 Feb 201806:52:24 +0000

MIME-Version: 1.0

Content-Type: text/plain

Date: Thu, 15 Feb 201806:52:24 +0000

Message-ID:

     <mailto:TY1PR0301MB1216BF2F3583070B7CBC018085F40@TY1PR0301MB1216.apcprd03.prod.outlook.com

 

- I've checked the Exchange admin centre > Protection and there is no entries for the effected user. 

- I've been through the process here: https://sender.office.com and advised our IP address is not effected. 

 

Please help! 🙂 

exchange
office 365

2 Replies

  • Brian Reid's avatar
    Brian Reid
    MVP
    Feb 15, 2018
    You need to raise a support call with Microsoft to get unblocked. You also need to implement MFA on all accounts to protect against this happening again. If you have EMS or AADPremium licences you can configure MFA only to trigger on external networks if you want to allow passwords only when authenticating from the LAN
    • Brad Hawkins's avatar
      Brad Hawkins
      Copper Contributor
      Feb 15, 2018

      Thanks Brian, 


      I have a request with MS so hopefully they get back to me today. 

       

      Cheers

      Brad