Formatting problem send_mail in version 2.10.0

I have recently switched to openSUSE Leap 42.2 and found that some of the features of send_mail no longer work. The problem occurs when trying to add information to a Cc to Stable.

The initial pass through the patch produces the output (body) Adding cc: Stable <stable@vger.kernel.org> [4.8+] from line 'Cc: Stable <stable@vger.kernel.org> [4.8+]'

That is correct, but the actual Cc list contains
         Stable <stable@vger.kernel.org[4.8+]>,

The mangled address is not legal and the mail attempt fails.

Thanks,

Larry