Hi Dov Brill,
As I understand, you are using Office 365 small business service and user account email address with custom domain. When other people send email to you, you can receive email from Gmail address normally. However, the sender got a Non Delivery Report (NDR) when some people send email to you. Some senders didn’t get the error message.
To narrow down the issue, please refer to the following information:
1. Try to add these email address to safe sender list. You can refer to
safe lists.
2. If you are using Outlook client, please try to go to Outlook Web App (OWA) to check if you can receive these email normally.
3. Moreover, could you please provide some detailed information about the NDR for further research? I will send you a private message. Please check the private message that has a subject of collect information.
• Go to the Your details section on the right side of the community site.
• Click Private messages.
• Click the subject title of the response to read the message.
• You can reply by using the form in this display.
• Click Submit Reply.
Thanks,
Ida Qiu
