Mail distortion when auto-forwarding by CRM

When sending a mail to CRM about new case for filing, the mail is successfully filed in Communications and auto-forwarded (by CRM) to assigned user for his information. The filed mail looks nice when looking its content in CRM, but when the assigned user opens the auto-forwarded mail in some mail agent (Outlook, for example), SOMETIMES its content is distorted - fonts are very large. I found that this happens in cases, when font size is given with a "." (dot) symbol, e.g., if the font size is set to "15.5", the CRM sometimes ignores that "." symbol and presents font with size "155".

Note that this issue happens not always - we have mails that also have font sizes with "." symbol and they are handled as expected.

So, what can be a reason of this issue and how it can be fixed? Note that we are using CRM 7.1.

Thanks.