Custom actions are not available in the Essentials solution.
If you need to grant SendAs/SendOnBehalf to Microsoft 365 groups, you can use the following script:
In PowerShell:
You use the GrantSendOnBehalfTo parameter on the various mailbox and group Set-cmdlets to manage the “Send on behalf” permission for mailboxes and groups:
Set-Mailbox-
Set-DistributionGroup(distribution groups and mail-enabled security groups) Set-DynamicDistributionGroup-
Set-UnifiedGroup(Microsoft 365 groups)
<Cmdlet> -Identity <MailboxOrGroupIdentity> -GrantSendOnBehalfTo <Delegates>You use the Add-RecipientPermission and Remove-RecipientPermission cmdlets to manage the “Send as” permission for mailboxes and groups
<Add-RecipientPermission | Remove-RecipientPermission> -Identity <MailboxOrGroupIdentity> -Trustee <DelegateIdentity> -AccessRights SendAsIn a CoreView custom action:
{
"id": "8cce8353-ddee-4d44-a824-f52f329cf70f",
"title": "Exchange - Grant SendAs/SendOnBehalf on M365 groups",
"lastModified": "2022-05-16T12:29:45.4590000Z",
"target": "None",
"tags": [],
"vars": [
{
"name": "M365groupemailaddress",
"type": "string",
"isRequired": true
},
{
"name": "Right",
"type": "list",
"values": "SendAs,SendOnBehalf",
"isRequired": true
},
{
"name": "User",
"type": "string",
"isRequired": true
}
],
"params": [],
"columns": {},
"version": 4,
"statement": "param ([string]$M365groupemailaddress, [string]$Right, [string]$User)\r\n\r\nif($Right -eq \"SendAs\"){\n Add-RecipientPermission $M365groupemailaddress -AccessRights $Right -Trustee $User -Confirm:$false\n}\nelseif($Right -eq \"SendOnBehalf\"){\n Set-UnifiedGroup -Identity $M365groupemailaddress -GrantSendOnBehalfTo @{add=\"$($User)\"}\n}"
}