Regarding Email Zabbix actions:

Because a trigger can refer to more than one item I use following format for mail notifications:

{ITEM.NAME1}: {HOST.NAME1}: {ITEM.KEY1}: {ITEM.VALUE1}
{ITEM.NAME2}: {HOST.NAME2}: {ITEM.KEY2}: {ITEM.VALUE2}
{ITEM.NAME3}: {HOST.NAME3}: {ITEM.KEY3}: {ITEM.VALUE3}

But when notifications arrive from a trigger that uses only one item, the unused ones are shown as *unknown*.
That looks IMHO a ugly and misleading - and apparently my Email client (Thunderbird) interprets ** as bold text, so the unknown items appear visually more important than the rest of the mail.

I have several proposals to solve this:

• introduce special characters that evaluate the containing macro only if it is defined, e.g.: ?{ITEM.NAME2}? would return nothing if {ITEM.NAME2} is not defined

• an interpreter, so we can use logic, e.g.:
  if {ITEM.NAME2} then print {ITEM.NAME2} end
  this could be covered by ZBXNEXT-1444

• a function that returns a list of defined Macros, e.g.
  table({ITEM.NAME},{HOST.NAME})

• make the returned string configurable, so instead of *unknown* we could choose to return an empty string