The Work-.CorrSend activity should be able to send email. Could you clarify why you need specifically to use SendEmailNotification Activity?
If indeed there is no other way than to use SendEmailNotification activity, then I believe your blocker is that all these rules are final so you can't overwrite them.
At this stage, check with UI designer if you can change the activity pzCreateOperatorAndSendEmail (presumably called from a control in a section) to a different custom activity which will meet your needs.
Before loading the UI for sending email, we run D_pzSMTPConnectivity data page in the background(in pzBuildApplicationDefaults activity) to check if the Default email account is configured. This Data page takes more than 10 secs to execute, so in step 11 of pzCreateOperatorAndSendEmail, we wait for 10secs and fail if the call takes more than 10 secs. We dont send the email if the email account is not configured or if the data page loading takes more time.
Could you private edit pzCreateOperatorAndSendEmail and increase the wait time in step 11 and see if the issue is with data page load.