I am using customized mailrules for some time, motivated by Chris Linfoot and dominopower.

These customizations add several conditions to the template.
I was looking for a way to customize actions and customized the servers names.nsf even more.

First Task: Add an action to change the message importance
This action is available in the client mailrules but not for server mailrules. In fact, it is there but just hidden in the GUI.

1. Edit the Form (RulesDlg)
2. add "change message importance |2" to the combobox "action".

This one was easy, wasn't it? Want to do more?

Second Task: Add an action to add a field

1. Edit the form (rulesDlg)
2. add "add field|X" to the combobox "action"
3. add two fields "AddFieldName" and "AddFieldText" below of "behavior". Change the hidewhen formulas to "!@Contains(action;"X")"
4. Edit the ScriptLibrary "Rules"
5. In the Declarations add
Const ACT_AddField = &h00000331&
Dim ACT_sAddFieldName As Variant
Dim ACT_sAddFieldText As Variant
6. In the Function "ActionString" add
Case "X"
ActionString = GetString(ACT_AddField)
7. In the Sub "GetGlobalActionValues" add the lines
ACT_sAddFieldName = Note.GetItemValue("AddFieldName")(0)
ACT_sAddFieldText = Note.GetItemValue("AddFieldText")(0)
8. In the Sub "ActionParser" add
Case "X"
s_MAINFORMULA = s_MAINFORMULA+"@setfield("""+ACT_sAddFieldName+""";"""+ ACT_sAddFieldText + """)"
9. In the function "GetString" add
Case ACT_AddField
GetString = " Add " + ACT_sAddFieldText + " to field " + ACT_sAddFieldName