Hi @Bimal Karki
Do you mean MailContact not showing in GAL?
You could check using this command:
Get-MailContact <contact alias> | fl *hidden*
The HiddenFromAddressListsEnabled parameter specifies whether this recipient is visible in address lists. Valid values are:
$true: The recipient isn't visible in address lists.
$false: The recipient is visible in address lists. This is the default value.
Set-MailContact <contact alias> -HiddenFromAddressListsEnabled $false
If that's not your case, please correct me and share more information.
In addition, I would like to remind you that Exchange 2010 has end support, it's better to migrate your server to a new version or O365 to get better experience and support.
Details: Exchange 2010 end of support roadmap
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