USG210 - No “Content-Type: text/plain;” header in email report.

My firewall (USG210) sends me logs via e-mail. They are e-mails in TXT mode.
The email program receives them and reads them correctly. But the anti-spam program (MailWasherPro) cannot display the contents of these e-mails (even though the source code is displayed correctly).
In my opinion, the reason for this is that the headers of the e-mails are missing the entry:

Content-Type: text/plain;

I would very much appreciate if you could correct this in a future update.

It is about this report:

Regards
Wojtek