![User receive the following NDR trying to send email from Exchange Online: 550 5.1.8 Access denied, bad outbound sender. - ThatLazyAdmin User receive the following NDR trying to send email from Exchange Online: 550 5.1.8 Access denied, bad outbound sender. - ThatLazyAdmin](http://www.thatlazyadmin.com/wp-content/uploads/2018/06/word-image-15.png)
User receive the following NDR trying to send email from Exchange Online: 550 5.1.8 Access denied, bad outbound sender. - ThatLazyAdmin
![5.7.1 <kxxxxxx@verizon.net>: Sender address rejected: not owned by user cxxxxxxxx@verizon.net. | Thunderbird Support Forum | Mozilla Support 5.7.1 <kxxxxxx@verizon.net>: Sender address rejected: not owned by user cxxxxxxxx@verizon.net. | Thunderbird Support Forum | Mozilla Support](https://assets-prod.sumo.prod.webservices.mozgcp.net/media/uploads/images/2016-08-23-06-19-42-140f14.png)
5.7.1 <kxxxxxx@verizon.net>: Sender address rejected: not owned by user cxxxxxxxx@verizon.net. | Thunderbird Support Forum | Mozilla Support
![550 5.1.8 Access denied, bad outbound sender AS(42003) – Brian Reid – Microsoft 365 Subject Matter Expert 550 5.1.8 Access denied, bad outbound sender AS(42003) – Brian Reid – Microsoft 365 Subject Matter Expert](https://c7solutions.com/wp-content/uploads/2021/03/image-14.png)