Even though other functionality of the CRM are improved over the last version updates, email templates remains the same for CRM 4.0, 2011 and 2013 which only allows you to create an entity-specific template for a limited system entities.
To overcome that issue, all of the custom entity related e-mail templates are just configured in workflows and the maintenance of the e-mail template is a bit tough. Moreover, in order to allow the users to modify the templates without missing out any event during the workflow deactivation, we need to them according to the High Availability Workflows article of MVP Dave Berry.
So, the number of workflows are getting more and more since there is one dispatcher workflow and each child workflow is required for each e-mail template which resulted in almost a hundred workflows in the system.
Finally, Ramon Tebar came up with a solution called Dynamics CRM Custom Email for Microsoft Dynamics CRM 2013. This utility provides several capabilities to extend the email functionality of the platform based on supported customizations such as ability to create Email Templates for custom entities, ability to reuse attachments from different templates, etc.
But due to the SDK assemblies used to build the DLL, neither the solution nor the custom workflow DLL cannot be imported/registered to the CRM 2011 organisation. Upon asking for the possibility of porting the solution for CRM 2011, I got a reply that it won't support CRM 2011 due to their project roadmap.
So, I just downloaded the source code of the solution in the CodePlex site and recompile it with CRM 2011 SDK DLLs according to his suggestion and then, merged DXTools.CRM.Solutions.CustomEmails.Workflows and DXTools.CRM.Solutions.CustomEmails.Common assemblies using ILMerge. After registering the merged DLL and tested on CRM 2011, it's working fine exactly as how it works on CRM 2013. Please refer to the Documentation section of the project to learn more about how to use it.
I've just exported the CRM 2011 compatible DLL as a solution for you to download and import the utility directly on CRM 2011. But in case if the Dynamics CRM Custom Email release the newer version and the one that I uploaded (currently version 18.104.22.168) is outdated, you may follow the steps above to recompile by yourself.
Disclaimer: The uploaded DLL is just a recompiled version for CRM 2011 without any modification to the source code and I take absolutely no responsibility for the content or functionality of any of these files. Once again full credit goes to Ramon Tebar and whoever contributed in Dynamics CRM Custom Email project.