Event ID 2009 when sending from mail-enabled public folder

Hi.

Whenever a user sends an e-mail from a mail-enabled public folder, we get event ID 2009 in the eventlog on the server.

Here is an example:

[Process:Microsoft.Exchange.RpcClientAccess.Service PID:8508 Thread:21] Error occurred while resolving the Active Directory object for from email address field: '/CN=Mail Public Folder/CN=Version_1_0/CN=e8220731-f0fa-4ddc-8468-b4c0b03fd014/CN=00000000F9EEE5CC0E1CEA4399F554BE45C282950100553B1102F06969459294143534D98B4D0001030A79E30000'. Audit log will not be generated for this case. Exception details:
Microsoft.Exchange.Data.Storage.ObjectNotFoundException: The Active Directory user wasn't found.
   at Microsoft.Exchange.Data.Storage.ExchangePrincipalFactory.FromProxyAddress(IRecipientSession session, String proxyAddress, RemotingOptions remotingOptions)
   at Microsoft.Exchange.Data.Storage.ExchangePrincipalFactory.FromProxyAddress(ADSessionSettings adSettings, String proxyAddress, RemotingOptions remotingOptions)
   at Microsoft.Exchange.Data.Storage.ExchangePrincipal.FromProxyAddress(ADSessionSettings adSettings, String proxyAddress)
   at Microsoft.Exchange.Data.Storage.COWAudit.GetSubmitEffectiveMailboxOwner(MailboxSession session, CallbackContext callbackContext)

The mails are sent correctly, but transport rules are not applied to them. So as we have some transport rules that copy mails with specific recipients, this is a problem.

The only references I can find to this error are related to not being able to send to the folder, and does not seem to apply to my situation.