The list or group you selected can't be expanded because it's too large

Question

Hi all,
Today I noted this trouble using MS Exchange OWA
Company is running Exchange Version 15.1 ‎(Build 2507.6)‎

I wrote an email and the recipient was a distribution group.
This distribution group is made by 210 users.

I tried to expand (I pressed on "+" button) but I could not see distribution group members, in fact I got this error message:
"The list or group you selected can't be expanded because it's too large".

Is there a way to solve it?
Employees use e-mail just from OWA, so I need to solve this issue for OWA client.

If distribution group is smaller I don't get this warning.

Thanks a lot

Answer 1

Check if the group was composed of outside organization contacts. It might be some contacts hidden there. Try to unhide and then check.

Answer 2

Hello,
In this moment I did not found any "outside organization contacts" member of this distribution group.
How can check it properly?

In this moment company has got hybrid environment, in other words company is starting to move some mailboxes from on-premise server to Exchange Online.
We don't experiencing this trouble if I use Exchange Online OWA.

Any other suggestions?

Thanks