External Contacts in Distribution list not populated in Outlook

[Biju Daniel]

We are an O365 Environment, Exchange Online. We have On-Prem AD and get synced to cloud.  We have distribution lists with external contacts . When we sent email through Outlook or OWA, when we expand these distribution lists external contacts are not visible.  External contacts are receiving emails.

We unhide the  external contacts in AD and still it is not getting populated.

Any idea's ?

[#2]

I'm not sure I completely understand the above, but I don't seem to have any trouble viewing external contacts that are added as members of a DG when I press the "expand membership" button in either OWA or Outlook. Nevertheless, if you can reliably reproduce this, open a support case.

[#3]

A couple things. Are the contacts synced to your 365 directory? My guess is the distribution group and contacts live on prem. So when you send e-mail to the group, the local on-prem server processes the group and sends the e-mail to all recipients. However your mailbox users are in 365 so when they look at the group they will only see the synced recipients in the group.

Anyway, bottom line, check to see if your contacts in that group are synced, betting that OU is selectively not syncing up to 365 that contains those contacts.

[#4]

Our External Contacts are Synced to Cloud. We create the External Contacts in ON-PREM AD and get it Synced to Cloud.

[#5]

So if you go to Microsoft 365 admin center > Users > Contacts you can find the contacts that are in that dist. group?

[#6]

Also you said those contacts were set as hidden from address list? When did you change those? If it was recent, it will take time for that to propagate and update the offline address book sync.

[#7]

@Chris Webb 

Our Contacts were Synced to Cloud. Our External Contacts were hidden  from GAL, but it was set to unhide recently

[#8]

it can take a few days for your outlook clients to reflect that change. You can go check the dist. group in OWA and see if it's updated there?

[#9]

I know this is a late reply but this is for anyone else that finds this topic.

I had the same issue and it was because the External Users were hidden from my organisations global address list.