We do not have high expectations for the outcome of the filesystem check, so we've deployed a new DE IMAP server and have re-created all DE mailboxes as new empty mailboxes on that server.
Customers should now be able to log in to our DE mail services to send and receive new mail. No changes to your email client settings should be required.
We'll begin restoring the original mailbox contents ASAP from the most recent backup made on 30 March 2022 (the failure occurred while the 31 March backup was still in progress). The restore may take several days to complete, so we'll keep this post updated until it is done.
We'll attempt to recover mail from 31 March 2022 when the filesystem repairs on the failed server are complete.