emailexchangemicrosoft-office-365
I notice there is a retention tag can help you move emails from recoverable items folders in main mailbox to recoverable items folders in archive mailbox.
May i know default how long can it stay in recoverable items folders in Archive mail box? How to change it? Any maximum limit? Thanks! Sorry to ask this silly question, I just cannot find a Microsoft explanation.
Users are still able to delete messages, and this is the most likely cause of the missing messages.
Retention Policies are used to "expire" items based on certain criteria, but they will not prevent objects from being deleted by a user.
In Office 365 if you need to prevent users from deleting messages you need place a hold on the mailboxes. You can define periods of time the holds are active, after which messages can be deleted, or leave it on indefinitely.
Based on the NDR messages, it seems to be generated from your on-prem Exchange server(server1.domain.com), right?
Did you enable centralized mail transport? Could you find this email on your on-prem Exchange server if you perform a message tracking:
Get-MessageTrackingLog -EventId RECEIVE -Source SMTP -Sender <Sender@domain.com> -Recipients <Recipient@domain.com> -Start "<Start Time and Date>" -End "<End Time and Date>" -MessageSubject <Subject> | Sort-Object -Property @{Expression = "Timestamp"; Descending = $false} | ft Timestamp, EventId, Source, Sender, Recipients, MessageSubject, ConnectorId -AutoSize
If there is an entry with a connector which received this message, maybe the following inspections are helpful:
Run the following command to check the connector's recipient limit: Get-ReceiveConnector -Identity "<ConnectorId>" | fl MaxRecipient*
If the limit is lower than the recipient count(469), try adjusting it with a larger number(e.g. 500): Get-ReceiveConnector -Identity "<ConnectorId>" | Set-ReceiveConnector -MaxRecipientsPerMessage 500
Then adjust the organization recipient limit: Get-TransportConfig | Set-TransportConfig -MaxRecipientEnvelopeLimit 500
Finally, restart MS Exchange Transport service on on-prem server and send emails again to see if there is any difference.
Best Answer
If you've permanently deleted an item in Microsoft Outlook or Outlook on the web (formerly known as Outlook Web App), the item is moved to a folder ( Recoverable Items > Deletions) and kept there for 14 days, by default. You can change how long items are kept, up to a maximum of 30 days.
To change the retention periode to 30 days you simply use the Set-Mailbox command in PowerShell when logged onto the Exchange Online Tenant:
For more information on the topic check the Microsofts docs page