RE: Workforce management for emails
I am the Solution Architect for the Genesys WFM Solution and I think I might be able to provide you some insight into what you are trying to do.
Firstly, when you say "turnaround time" is 24 hours from receipt, does that mean that the email must be delivered to an agent within 24 hours or that the issue communicated in the email must be resolved within 24 hours. Technically speaking, the difference is between "wait-time" and "handle-time".
Traditionally, WFM forecasted staffing needs focus more on the "wait-time" statistic more than the "handle-time" statistic. "Wait-time" is directly related to the service-level/ASA factor that is input into a required staffing algorithm; This responds to the question, "How quickly to I want my emails delivered to an agent?"
The "handle-time" issue is usually addressed via training or CRM applications: Ways to help the agent process the customer's email more quickly once it is ALREADY delivered to them. In your situation, your forecasting needs to focus on that 24 hour factor, since it only takes 5 minutes for the agent to handle the email once it is delivered to them.
Now, I do not know the capabilities and limitations of the current products you are using, however, I can tell you that their are very few workforce management applications that are integrated and provide accurate WFM functionality for emails. Not only do most WFM applications provide any kind of interfacing to email-distribution systems, but they don't provide the proper forecast staffing algorithms for work-types such as email.
Email is a deferred response interaction. Voice calls are an IMMEDIATE response interaction. For voice calls, and other work like it, the customer is live and actively waiting for you to respond to them; Service Level requirements for these types of interactions are along the lines of x% in y seconds, or an ASA of # seconds. Email and other deferred interactions are usually measured in terms of 100% in x HOURS, as is the case with your environment. All standard staffing algorithms are going to be based around Erlang-c. Erlang-c was designed specifically for IMMEDIATE response work types. If you try to enter "100% in 86400 seconds (24 hours)" into an Erlang-c based algorithm, it will fail. Erlang-c was not designed to be able to accurately handle Service level time thresholds of that magnitude. You need to make sure that your forecasting algorithm that you are using for your email work is not based on Erlang-c.
Unless you are running a workforce management system that is providing these two capabilities, you are going to end up doing a LOT of work manually.
One of the very few workforce management systems in the world that actually does both of these is the Genesys WFM Solution. I highly recommend you take a look at it. I don't want this reply to turn into a commercial for the company I work for, but I did want to try to address your problems and provide you with a possible solution.
Please feel free to contact me should you want more information on what Genesys can do for you and your email staffing situation.
WFM Solution Architect