Is it bad to mount a rack mountable server vertically?

We are moving to an office with a server closet that may not have sufficient depth to have a standard server rack. I found a vertical rack mount online (that mounts to the wall) that is 4U. Are there negative effects to mounting servers vertically instead of horizontally?

Certain specific case designs may have issues with mounting in other-than-horizontal attitudes, but there isn't anything inherent to server cases that would suggest this is bad. Bad case-designs would have parts vibrating loose after long periods without gravity to retain them, but this shouldn't be a problem with a major server vendor case. Most blade-servers are vertical in my experience!

Check the venting path. Hot air should not get trapped in a 'dead end' at the 'top' of a horizontal case mounted vertically. If there is room for air to be sucked in and then blown out having passed over most of the PCBs you will be ok.