New Distribution List Group won't receive emails from external address

[justin1981]

I am having trouble getting a new Distribution List group to work properly.  I have setup in the admin portal under groups the distribution group email/alias, etc, and have checked the option "Allow External Senders to Email this Group".  I verified a couple of times this box is in fact checked. 

Everything is saved and its been a couple hours since setup.

When I send an email from my internal address to the distribution list address, it works fine - the distribution list delivers to the distribution list members.  However, if I send to the list email address from an external address, I get a bounce back error "553 sorry, no mailbox here by that name. ulc: , rcp: 0001. (#5.7.1)" and no message is delivered.  

Does it take time for things to propagate through the DNS or AD or something?  In AD control, the distribution list shows as active and running.  It works fine as I said internally... it just won't work for external email addresses... which is a requirement for what I am trying to do with it. 

Any thoughts or suggestions?  

[#2]

Hi all, just wanted to add what I had to do, in case it helps someone else. I created the dist list and for 2 weeks I wasn't receiving external email even though I selected "Allow External Senders to Email this Group". I had to uncheck it, then save and recheck it. After that, it started working.