Folks, Most likely not the culprit, but thought I would share anyway - just ignore if you already know it isn't due to this - this is something I encountered with trying to restore mail to mailboxes. Just pasting in my notes that I took at the time: "Some mail will not restore to mailbox, and you get a forwarding loop for the user (note that you always get a forwarding loop for bcc the archive blind copy, this is OK just ignore the message. It stops the restored mail getting added into the archive again anyway). This happens because of the Delivered-To header. Postfix adds this header, and as there may already be one there with the same recipient, it thinks the restored mail is in a mail loop and you get the error (and no mail). The quick workaround is to add a header check for the user, e.g.: /^Delivered-To: m.gras...@asb-group.com/ IGNORE add this to /etc/postfix/header_checks on the mail server Remember to postmap the file after editing it." ------------- This email and any attachments are confidential to the intended recipient and may also be privileged. If you are not the intended recipient, please delete it from your system and notify the sender. You should not copy it or use it for any purpose nor disclose or distribute its contents to any other person. -----Original Message----- From: Martin Nadvornik <martin.nadvor...@diakonie.at> Sent: 27 April 2021 14:24 To: Piler User <email@example.com> Subject: AW: Restore to O365 fails Hi everyone, we also have the same or at least a similar problem. However not with every mail but with most. We were so far also unable to find the root cause for this and can't see any distinctive differences between mails that fail to restore and those that don't. In our specific setup piler is using a postfix server as smart host which then redirects the messages to exchange online via a transport rule. EXO accepts the restored messages our postfix sends but never delivers them to the inbox. Looking at the message trace in EXO shows that the message is beeing recived but there are no detailed trace infos available. Out first guess was also that EXO doesn't like recveiving messages with the same message ID multiple times. We haven't tried REWRITE_MESSAGE_ID yet but based on what Alex wrote this seems to not solve the problem. Martin ________________________________________ Von: Karl Rossing <karl.ross...@gmail.com> Gesendet: Freitag, 16. April 2021 17:54 An: Piler User Betreff: Re: Restore to O365 fails We have had the same problem. I meant to open a ticket with Microsoft but so far have not. On Fri, Apr 16, 2021 at 8:53 AM Alexander Noack <a...@loetzimmer.de<mailto:a...@loetzimmer.de>> wrote: I do realize that this is very likely not a Piler issue but rather O365 related but maybe somebody already came across this issue and knows how to remediate it. When I restore a deleted email in my O365 account, the message transfer always fails: 550 4.3.2 QUEUE.TransportAgent; message deleted by transport agent The Piler server is setup as a connector in Exchange Online. The Smarthost is <tenant-domain>.mail.protection.outlook.com<http://mail.protection.outlook.c om>. Mails seem to be originating from MicrosoftExchange329e71ec88ae4615bbc36ab6ce41109e@<tenant>.onmicrosoft.com<h ttp://onmicrosoft.com> The error states that there is an NDR sent to that address, but even after assigning that address to myself, no NDR is ever received. I have set $config['REWRITE_MESSAGE_ID'] = 1; Any help is greatly appreciated! Alex Missiles & Space Batteries Limited is registered in Scotland under company number 162626. The company's registered office is at Hagmill Road, East Shawhead, Coatbridge, ML5 4UZ.