held at the window until the clerk collects it
A file that refused to open earns priority handling — say which program produced it and what the refusal said. Please don't forward the actual email unless it's truly nothing (the whole shop is built on not passing letters around); the header block with names snipped out usually cracks a charset case. Requests for .pst, winmail.dat and friends are votes, and votes get counted.
replies by return of post, in the old sense: reliably, and no faster than the sorting allows.