O365 distribution groups

[MobileTechie]

I've an O365 Small Business Premiumn client who want to have the address sales@theirdomain.com to go to several internal users.

One way of doing this seems to be to use a mail Distribution list which I've done - set up sales@theirdomain.com and added the users to the list.

I've ticked the box to allow external users.

External mails sent to this address do not arrive at list members' mailboxes and no error is received. Internal mails sent to this address do eventually get an error:

"Sales
The email address you entered couldn't be found. Check the recipient's email address then try to resend the message. For more tips to resolve this issue see DSN code 5.1.1 in Exchange Online. If the problem continues contact your help desk."

Have I missed something fundamental about how distribution lists work? Do they, for instance, require an actual mailbox for Sales to exist?

 

[wardoursecure]

When you say external I presume you mean you have checked allow senders inside and outside my organisation.
Have you made sure that message approval is unchecked?

 

[MobileTechie]

When you say external I presume you mean you have checked allow senders inside and outside my organisation.
Have you made sure that message approval is unchecked?

Yes I've ticked (checked in US) that box.

 

[MobileTechie]

Deleted them. Recreated them. Started working.