There is an updated pull request by rakoo against master on the mblaze repository

https://github.com/rakoo/mblaze master
https://github.com/leahneukirchen/mblaze/pull/258

contrib/mmailto: Fix using longer arguments
We put the args to $TERMINAL inside single quotes for terminals that want a single command, and we put arguments extracted from the adress between double quotes to protect from spaces.

This is necessary for `xfce4-terminal` for example, and doesn't break `xterm`

A patch file from https://github.com/leahneukirchen/mblaze/pull/258.patch is attached