Email-logo preview updating problem in Thunderbird


I just found out that there are problems in the logo updating-process in emails when using Thunderbird as email client. When the logo is changed, in Outlook all emails are updated with the newest logo. But in Thunderbird there are problems, e.g. only a colored bar or older logos are shown in the header.

Is this a kind of “chaching problem” in Thunderbird? Is there a solution?