Why won't Outlook cooperate with me when I want to schedule an email to be sent at a later date/time?

For one of my non-Fluther jobs, I’m using Outlook on a remote server. I do a fair bit of the work at night, but want my emails to go out during normal business hours. When I compose an email, I choose “options” then “delay send”, schedule it to go out the following morning, and hit “send”. Most of the time, this fails miserably, with only the occasional one actually getting sent out at the scheduled time. The rest just sit there in my out box, going nowhere!

Is this an Outlook issue, a remote server issue, a user error, or what? Is there a way to fix it?