All messages which are listed in your outbox are in the inbox of the recipient. Even if the recipient did not get an email, he will see them when he logs into ModularGrid.
A missing feature of the ModularGrid Messenger:
It's not possible to reply to ModularGrid messages from your email program. They go to noreply@modulargrid.net, which is a digital trashcan.
You have to log into ModularGrid and use the messenger there.
Beep, Bopp, Bleep: info@modulargrid.net