Outlook 365 client intermittent trouble expanding distribution group

Skip Honk 1 Reputation point

I have some users experiencing an intermittent problem expanding a distribution group in the windows outlook client. These are O365 accounts.

The DL is quite old, and has been working fine for most users for years. Recently some users started experiencing problems expanding the group. They do this sometimes to quickly send an email to a list of people and manually remove a few that do not need the email.

When they attempt to expand the group they get this error

I figured out a manual workaround when this happens:
-clear out the to: line
-go to the address book
-select "All Distribution Lists" from the dropdown
-select distribution list and click the "To" button
-this will populate the mail in a format that you can always expand

Once the manual dance is performed it will work fine for a while. Today it broke again after working yesterday for my favorite user. After the fix it works fine but will def break again soon.

Is there a better way to proceed than this ugly hack?

Outlook Management
Outlook Management
Outlook: A family of Microsoft email and calendar products.Management: The act or process of organizing, handling, directing or controlling something.
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  1. Jade Liang-MSFT 9,956 Reputation points Microsoft Employee

    Hi @Skip Honk ,

    What's the version of your Outlook client(File>Office Account>About Outlook), please ensure that you have updated to the latest version of Outlook.

    I have some users experiencing an intermittent problem expanding a distribution group in the windows outlook client.

    Considering the issue has been occurred only recently, have you performed any special operations before it?
    Did this issue only happen to any specific users? If so, are there any similarities with these users?

    According to your description, I understand that you could add the distribution list mannually via the address book. As I know, this error would dispaly if you insert a corrupted or unsuitable items via autocomplete list, and it's suggested to first delete this item in autocomplete list like below and resend the message via mannually add the list from address book to test, the new item would be added in autocomplete list again once you send the message, and then you could check if it could work normally with the new item.

    If the issue still exists, due to the issue only happened to a specific distribution list, it may be related to the list itself. Based on my research, I found a similar thread, which mentioned this issue would occur if you are in a multi-domain environment, if that's also your case, it's suggested to change the group type from Universal to Global as the thread mentioned to check.

    Also, if the issue only happen to few users and these users just would like to send message to a group, as an alternative, it's also suggested to create a local contact group mannually in Outlook(Contact>New Contact group>Add members), they could also expand and manage this group in their Outlook.

    Hope that would be helpful to you, and if your issue has any update, please feel free to post back.

    If the response is helpful, please click "Accept Answer" and upvote it.
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