I have a list of departments and their IT support email address. What I would like to do is in the process if the email is Null it sends to our IT department and if it is populated it sends an email to the email address listed (which are about 26 different emails). Would it be better to do this in a calculation (if so how) or should I just list them all as decision or precondition.
773 allows you to send things to an external email address which is a really great feature. Prior to that you cannot send messages to hand coded email addresses, only to specific LDSD created groups/users. (Well you can with a Response Level escalation action, but that's not the point)
You could create a group and put those 26 people into it and check the receive email group check box. Send the reminder to the group and they will all get it.
Personally I'd do it as a condition and then send the reminder to either one group or another