My normal mail view in any email client shows all the mail headers making it difficult to read
Certain mail I view using either the web client or a desktop client like Thunderbird, MS Outlook, I see all the message headers in the message area, making it very difficult to decipher and read the mail.
Why does this happen? Is there a problem in my client?
If the mail is not showing properly in multiple clients, it indicates that the mail is malformed by the sending client. Its quite possible that an important header or section closure tag is missing, which causes the mail client to show it mal- formed.
Mail clients are designed and tested to show valid MIME format mails. They also make fair amount of corrections to compensate for several common differences in the formatting. However if the mail has some critical tag missing, the mail client wont be able to show it properly. It then shows you the best possible view so that you can at least see the mail in some form.
Unfortunately there is not much that you can do about this, besides informing the sender about this. They can take some corrective action at their end in the client software.