It can happen when you import messages from somewhere and the message source has an invalid date format or value. When eM Client saves those messages to the server, the server objects to the date.
Clicking on Ignore will only ignore the issue until eM Client tries to upload them to the server on the next sync. Then the server objects again and you get another error.
You can try move them to Local Folders, so they are not synced with the server, otherwise you will need to delete them.
Thanks for the reply! The 14 are all in sub-folders of “Local Folders” & relatively easy to find since the date is something like “Sat 08:05 AM”. If I happen to know the exact date of the email, is there anyway to change the date or is deleting them the only way?