Why are journal reports archived from Office 365 to Proofpoint Essentials being bounced back with '554 Mismatch in o365 allowed address'?

This bounce occurs when the Undeliverable Journal Address set within the Essentials Archive connection settings does not match the email address that the journal reports are sent from.

You can resolve the problem as per the steps below:

1. Login to the Office365 ECP: https://outlook.office365.com/ecp/
2. Select Compliance Management > Journal Rules.
3. Beside Send undeliverable journal reports to: click on the hyperlink and select an account to send to (Note: the address used will receive journal reports in the event of the archive service going down or being unavailable. Therefore it's best to use a dedicated account as you will need to retrieve these journal reports over an IMAP connection in such a scenario. An address ending in .onmicrosoft.com should also not be used).

Now check the archive connection within the Proofpoint Essentials Archive matches:

1. Login to the Proofpoint Essentials management console with an Org Admin account.
2. Click Archive.
3. If prompted, select LAUNCH EMAIL ARCHIVE.
4. Click on the cog icon and select Connections.
5. Edit the Office 365 connection present.
6. Make sure the Undeliverable Journal Address matches that set within Office365.