How do I stop this problem: Sender and content in email do not match as this same content is a duplicate of recently send email.
Two email will arrive within a few minutes of one another. The first one is correct. That is, it is clear to me that the content comes from the sender. The next email, though, will have a new sender but the prior content is in the text and the new sender's text is not available...can't see it at all. This has happened a few times this year. Not often, but once is enough.
Has me worrying that my own content might go to the wrong sender no matter I place in the sender box. But, this is all secondary to the above issue.
Wšykne wótegrona (1)
This is usually a sign of folder corruption. Right click the problem folder and select Properties. Then Repair Folder.
Be prepared to lose messages if the corruption is too bad.
Read this article about maintaining your email system to help prevent this in the future. http://kb.mozillazine.org/Keep_it_working_-_Thunderbird