Fix #15667
With this PR:

The property-based API has been used. Added support for the
`informativeText` and `detailedText` properties.
Nice work!
I also wasn't aware of QMessageBox::setDetailedText().
utACK 2ee756f0411c467fc638373ea68d6cb5ced46974
Tested a bit. I think the "show details..." approach should only appear if we have multiple recipients. But I'm open to be convinced otherwise.
@promag @jonasschnelli Thank you for your reviews.
I think the "show details..." approach should only appear if we have multiple recipients.
Nice. Done.
code review ACK 78f9b5160fea32f85c6ced16b3b0cccda6d3b181