Send emails in the background

[st3iny]

Is your feature request related to a problem? Please describe.

When sending an email I have to wait for the modal to close.

Describe the solution you'd like

Ideally, the modal should close instantly and the sending or saving to the outbox should happen in the background. Given that we have the outbox, sending the email is delayed anyway.

A toast should be shown to indicate that saving the email in the outbox is in progress: Sending message... (3 seconds)

Describe alternatives you've considered

No response

Additional context

No response