Just filling in /usr/bin/mailx with "Open in terminal" checked works without problems ...
In operaprefs.ini
Code:
[Trusted Protocols]
mailto="0,1,"/usr/bin/mailx %s"
[Mail]
Webmail Service=0
External Application="/usr/bin/mailx %s"
Handler=2
And in [User Perfs]:
Run Email In Terminal=1
(Asked Admin to move these posts to a new thread btw.)