I know... When I noticed that Opera 12.0 (with several tabs open and being set to "Work Offline" before closing it) asks me for EVERY tab whether I want to go online, I decided that I will never update it anymore. Maybe I will switch to firefox later on.
And I have the same behavior as Anglo. Or I had - NOW it works, regardless of the setting of "save a copy to my outbox" - a feature that I also see properly working for the first time.
Many thanks for fixing it to whoever did it!
UPDATE: I had JavaScript turned off. When I turned it on, I got the same problem as before - but it's not reliable anymore, a few trials later it workes with JS on and a copy in my outbox. So it's not yet perfect but much better already.
All this with Opera 11.64.