Symptoms

Client Event Notification Setting From Address cannot be defined
 

Diagnoses

Normally, Client Event Notification Setting From Address has default value from k2 system "From Address"
Now, The default value is dissappeared and we can't add any values/ drag other field to the From field

 

Resolution

From the Environment Fields page, the From Address is set to default, change it to the Mail Server resolved this issue:
1. Go to Environment Fields from K2 Workspace > Mangement > Management Console > K2 Server > Environment Library > Templates > Default Template > Environments > Production > Environment Fields
2. Select “From Address” field and edit it by unchecking “Set as default”
3. Select “Mail Server” field and edit it by checking “Set as default”