“No Sender, No Subject” emails after iOS 11.2.6 update

My iPad Pro updated to iOS 11.2.6 last night. Now several, but not all, of my mailboxes have these weird “No Sender, No Content” emails. The emails are dated 12/31/69. When I open the email it says ”No message selected.”. These emails are marked as new, stay new even when opened, and will not delete.

I tried 1) resetting the iPad, 2) turning each mailbox off, then on in Settings, and even 3) deleting and redownloading the entire mail app and reinstalling each mailbox. None of these options worked.

My iPhone X also updated last night and the same mailboxes on my iPhone are not showing these annoying “No Sender, No Content” emails.

Any help would be appreciated.

Thanks, Jo