Office 365 Group not allowing external senders - Accept Messages from all Senders is selected

I have created an Office 365 group. I am the owner.  It simply has 5 members and the goal is to allow customers to send an email to the address and have it distributed to the 5 members.

I have Accept messages from: All Senders selected and have Reject messages from: No Senders selected.  

Despite those selections no email addresses from outside the group can send emails to the group.  The following is bounced back to them:

Reported error: 550 5.7.193 UnifiedGroupAgent; Delivery failed because the sender isn't a group member or external senders aren't permitted to send to this group.


Question Info

Last updated July 12, 2019 Views 10,492 Applies to:

Hi Russell Conde,


Thanks for posting the issue you encountered in our forum. According to Report error in the non-delivery reports, you might not allow people outside your organization to send email to the group. Please make sure you have check the option “Let people outside the organization send email to the group” for the Office 365 Group. Please sign into your Office 365 portal and navigate Exchange Admin Center> recipients> Groups, then double-click the Office 365 Group you need to modify. At the bottom of  the “general”, please check the box “Let people outside the organization send email to the group”.



Please give it a shot and re-try sending email to the Group to see how it goes.



Best regards,


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