I get the above message when logging into emails.
It only started after I imported old emails into EMClient form other email programes.
Do you have any suggestions.
That sounds like a eg: badly corrupted email message or message folder, where it has lost the date header in one or more message fragments.
All I could suggest is to backup eM Client via “Menu / Backup” and then once backed up, delete and try reimporting those old messages or message folders again.
If still the same problem, try exporting your old messages to eg: .eml files “in your old mailer” and then drag those messages into eM Client manually “a group at a time” and close and reopen eM Client in-between doing that.
When you then get up to the problematic message or messages causing the error, skip those messages or messages. You can then look at hopefully repairing those messages externally and then dragging them in later.