Group Won’t Accept Mail From ‘Outside’

KB ID 0001771

Problem

Exchange has been this way for a long time here’s me explaining this very problem with older versions of Exchange. If you create a ‘Group’, be that a Distribution Group, or a ‘Microsoft 365’ Group, the default setting is to NOT ALLOW mail from anyone outside your organisation. If you attempt to send mail to that group you will see errors like these;

Only Accepts Messages from People in

Errors;

550 5.7.133 RESOLVER.RST.SenderNotAuthenticatedForGroup; authentication required; Delivery restriction check failed because the sender was not authenticated when sending to this group

550 5.7.133 RESOLVER.RST.SenderNotAuthenticatedForGroup; authentication required; Delivery restriction check failed because the sender not authenticated when sending to the group’

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.

Allow External Senders (On Premises & Hybrid Exchange)

If you have your own on premises Exchange server, this includes those of you that have migrated to Exchange online, but are in Hybrid Mode and are syncing your domain objects into Microsoft/Office 365 (Azure). Then you should change this setting in the on premises Exchange Admin Centre.

Recipients > Groups > Select the group in question  > Edit > Delivery Management > Change to ‘Senders inside and outside of my organisation’ > Save.

Allow External Email to Group

Note: Remember in hybrid mode this will need to sync to Microsoft online, so apply the ‘cup of coffee rule’ before testing it.

Allow External Senders Office/Microsoft 365 (Exchange Online)

Classic Exchange Admin Center

Recipients > Groups > Select the group in question  > Edit > Delivery Management > Change to ‘Senders inside and outside of my organisation’ > Save.

 

Office 365 Allow External Email to Group Classic

New Exchange Admin Center

Microsoft 365 Groups: Recipients > Groups > Microsoft 365 > ‘Double Click’ the group in question > Settings  > Allow external senders to email this group > Save.

Microsoft 365 Allow External Email to Group

Distribution Groups: Recipients > Groups > Distribution List > ‘Double Click’ the group in question > Settings  > Edit Delivery Management.

Exchange Online 365 Allow External Email to Group

Allow messages from people inside and outside my organisation > Save changes.

Exchange Online 365 Allow External Email to Group

Related Articles, References, Credits, or External Links

NA

Author: PeteLong

Share This Post On

Submit a Comment

Your email address will not be published. Required fields are marked *