Can't get rid of IMAP warning about moving a message to the Sent Folder because too large

Each time I open eM Client I get an error pane with the message :
E-mail Providers name: Error Occured (title)
[IMAP] It is not possible to upload message “title message” to the Sent folder. (Message size exceeds maximum message size limit)

I can ignore but every restart of the application I get the same error message.

I looked into all my folders, also local, but I cannot find that particular message…

In the logging I see: MailClient.Storage.Application.OperationException

“(Message size exceeds maximum message size limit)”

This message it ́s clear

Have you active the “LOCAL Folders” (Setting>General>Gerneral>“Show Local folders”), also not only the IMAP LOACL Folder at EMC! And show in this SEND Folders?

Yes, the local folders are present and empty