Short answer:
Microsoft 365 Groups only allow internal senders by default. Since Xink reroutes emails, messages may be blocked. To fix this, either allow external senders or exclude Microsoft 365 Groups from rerouting.
By default, Microsoft 365 Groups only accept emails from internal senders.
When Xink server-side rerouting is enabled, emails are processed externally and then returned to Microsoft 365. As a result, these messages may be treated as external and blocked by Microsoft 365 Groups.
You can resolve this in two ways:
- Allow external senders for the group
- Exclude Microsoft 365 Groups from rerouting
Option 1 – Allow external senders
Allowing external senders ensures that rerouted emails are accepted by Microsoft 365 Groups.
Option 2 – Exclude Microsoft 365 Groups (bulk)
You can exclude all Microsoft 365 Groups from rerouting using PowerShell.
1. Open PowerShell with elevated permissions
2. Connect to Exchange Online
Connect-ExchangeOnline
3. Get the Xink transport rule
$XinkRule = Get-TransportRule -Filter "Description -like 'Xink-Auto-ReRouting-Catcher'" -State Enabled -ExcludeConditionActionDetails $false
4. Get all Microsoft 365 Groups
$GroupList = Get-UnifiedGroup -ResultSize Unlimited | Select -ExpandProperty Alias
5. Add groups as exceptions to the transport rule
$XinkRule | Set-TransportRule -ExceptIfAnyOfRecipientAddressContainsWords $GroupList
Note: Bulk exclusions are limited to 8192 characters. If you exceed this limit, consider splitting the exclusions or refining your transport rule conditions.
Recommendation
If you rely heavily on Microsoft 365 Groups, excluding them from rerouting is typically the safer approach. This ensures reliable delivery without changing group-level security settings.
