The default mail template isn't stored in the K2 database.  It's on your workflow server at the following location:

C:Program Files (x86)K2 blackpearlHost ServerBinSourceCode.EventBus.ClientRecorder.DLL.mailTemplate

Open it with Notepad to view the contents.  Make changes then restart the K2 service for them to take affect.

Note that this change emails for all processes running on your workflow server.  If you want to change the emails for a single process, you have to use K2's kludgy email templates within the activity.  They work, but they are a bit odd to work with.

BTW, you can find the K2 database ERD here.

I probably should have mentioned that the email item was customized. It is not a client activity notification event, but is an email event.

I probably should have mentioned that the email item was customized. It is not a client activity notification event, but is an email event.

Then you are SOL, sorry. :-)  Only option is to publish a new version of the WF with your changes.

I once had to do a large workflow where the client kept changing their mind about the contents of emails from the workflow.  Every time we met with them thy had changed their mind again and we had to touch every notification, escalation and activity in the email.  It was painfully brutal.

Email templates and notifications are one of K2's larger shortcomings, IMHO.  If you are going to have "templates," you need to be able to change the template and have it propagate to everything that uses that template.  There have been some third-party efforts to improve this, but none are very effective in my view.